arc supports kgdb, but need update -- add function kgdb_roundup_cpus(),
or can not pass compiling. At present, add the simple generic one just
like other architectures(e.g. tile, mips ...).

The related error (with allmodconfig):

  kernel/built-in.o: In function `kgdb_cpu_enter':
  kernel/debug/debug_core.c:580: undefined reference to `kgdb_roundup_cpus'
Signed-off-by: NChen Gang <gang.chen@asianux.com>
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>

With ECR now part of pt_regs

* No need to propagate from lowest asm handlers as arg
* No need to save it in tsk->thread.cause_code
* Avoid bit chopping to access the bit-fields

More code consolidation, cleanup
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>

pt_regs->event was set with artificial values to identify the low level
system event (syscall trap / breakpoint trap / exceptions / interrupts)

With r8 saving out of the way, the full word can be used to save real
ECR (Exception Cause Register) which helps idenify the event naturally,
including additional info such as cause code, param.
Only for Interrupts, where ECR is not applicable, do we resort to
synthetic non ECR values.

SAVE_ALL_TRAP/EXCEPTIONS can now be merged as they both use ECR with
different runtime values.

The ptrace helpers now use the sub-fields of ECR to distinguish the
events (e.g. vector 0x25 is trap, param 0 is syscall...)

The following benefits will follow:

(1) This centralizes the location of where ECR is saved and will allow
    the cleanup of task->thread.cause_code ECR placeholder which is set
    in non-uniform way. Then ARC VM code can safely rely on it being
    there for purpose of finer grained VM_EXEC dcache flush (based on
    exec fault: I-TLB Miss)

(2) Further, ECR being passed around from low level handlers as arg can
    be eliminated as it is part of standard reg-file in pt_regs
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>

  CC      drivers/mmc/host/mmc_spi.o
drivers/mmc/host/mmc_spi.c:118: error: redefinition of 'struct scratch'
make[3]: *** [drivers/mmc/host/mmc_spi.o] Error 1
make[2]: *** [drivers/mmc/host] Error 2
make[1]: *** [drivers/mmc] Error 2
make: *** [drivers] Error 2

  CC      arch/arc/kernel/kgdb.o
In file included from include/linux/kgdb.h:20,
                 from arch/arc/kernel/kgdb.c:11:
/home/vineetg/arc/k.org/arc-port/arch/arc/include/asm/kgdb.h:34:
warning: 'struct pt_regs' declared inside parameter list
/home/vineetg/arc/k.org/arc-port/arch/arc/include/asm/kgdb.h:34:
warning: its scope is only this definition or declaration, which is
probably not what you want
arch/arc/kernel/kgdb.c:172: error: conflicting types for 'kgdb_trap'

  CC      arch/arc/kernel/kgdb.o
arch/arc/kernel/kgdb.c: In function 'pt_regs_to_gdb_regs':
arch/arc/kernel/kgdb.c:62: error: dereferencing pointer to incomplete
type
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>

Signed-off-by: NMischa Jonker <mjonker@synopsys.com>
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>
Cc: Jason Wessel <jason.wessel@windriver.com>
Acked-by: NJason Wessel <jason.wessel@windriver.com>