* bsp beaglebone: add IAR template files and fix it's build error

ATTENTION:
project.* was generated by scons, so I add it to gitignore.
rtconfig.py *FLAGS located in "PLATFORM == 'iccarm'" are unverified and maybe wrong.
（我只是从STM32里面抄来，然后根据自己的理解改了一下，并没有验证这些参数的正确性，
我也不知道怎么用命令行调用这些参数来编译）

* bsp beaglebone: add beaglebone_ram.icf ROM address from uboot_cmd.txt

am335x_DDR.icf use 0x82000000, different to uboot_cmd.txt & gcc beaglebone_ram.lds,
the difference will easy cause later developer got below error:

=> go 0x80200000
## Starting application at 0x80200000 ...
undefined instruction
pc : [<8200956c>]	   lr : [<8ff62497>]
reloc pc : [<728a956c>]	   lr : [<80802497>]
sp : 8df37358  ip : 00000000	 fp : 00000002
r10: 8df4d448  r9 : 8df3feb8	 r8 : 8ffd30f8
r7 : 8ff78089  r6 : 00000002	 r5 : 80200000  r4 : 8df4d44c
r3 : 80200000  r2 : 8df4d44c	 r1 : 8df4d44c  r0 : 00000001
Flags: nzCv  IRQs off  FIQs on  Mode SVC_32
Code: 5dbffcdd bb9bdf7f abf85423 eff1f77f (7ed7daaf)
Resetting CPU ...

resetting ...

* libcpu am335x: context_iar.S rt_hw_context_switch: add thumb mode support

IAR new project defualt Processor mode is Thumb, this will cause user
easy occur the following error:
...
msh />Execption:
r00:0x8800aaa8 r01:0x802080c5 r02:0x00000000 r03:0x88009b4c
r04:0x00001000 r05:0x00000000 r06:0x00001403 r07:0x00100000
r08:0x00000000 r09:0x00000000 r10:0x0000000a
fp :0x0000000a ip :0x65687374
sp :0x00006c6c lr :0x0000008a pc :0x88008be0
cpsr:0x880001bc
software interrupt
shutdown...
(0) assertion failed at function:rt_hw_cpu_shutdown, line number:160

* bsp beaglebone: change IAR template.ewp code use Arm mode

Arm mode bin size will bigger than Thumb mode

* libcpu am335x: IAR: use rt_hw_cpu_dcache_enable instead of rt_cpu_dcache_enable

Reviewer mysterywolf say:
麻烦把rt_cpu_icache_enable 和 rt_cpu_dcache_enable, 统一改成 rt_hw_cpu_icache_enable 和 rt_hw_cpu_dcache_enable
rt_hw_cpu_icache_enable 和 rt_hw_cpu_dcache_enable 是其他bsp也是这么命名的 这是个命名统一的函数