The recent commit "serial: add irq handler for Freescale 16550 errata"
would allow Kconfig choices that had 8250 support as a module and
yet still try and build in the errata fix non-modular, resulting
in build failures for some non-embedded PPC targets.

Since we hook in the errata fix from legacy_serial.c, which is
built only for PPC_UDBG_16550, and since the errata is only really
relevant for SysRQ on serial console, tighten up the dependencies
to be exactly that.

We'll get coverage on the relevant Freescale boards because the
Kconfig for their CPU types all select the PPC_UDBG_16550 option,
and the defconfigs also all select the 8250_CONSOLE option.  Also,
the 8250_CONSOLE option has a strict dependency on "SERIAL_8250=y"
which resolves the reported problem for non Freescale targets.
Reported-by: NMichael Neuling <mikey@neuling.org>
Signed-off-by: NPaul Gortmaker <paul.gortmaker@windriver.com>
Tested-by: NMichael Neuling <mikey@neuling.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>