ARM: mxs: select STMP_DEVICE and use it for timer code

Select STMP_DEVICE and in timer code replace mxs_reset_block() with
stmp_reset_block(), use STMP_OFFSET_REG_SET/CLR to replace
__mxs_setl/clrl.

As the result, <mach/mxs.h> and <mach/common.h> includsion can be
removed from timer.c now.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>