Now when drivers/clocksource/Kconfig has been
updated with entires for CMT, TMU, MTU2, and STI
it is safe to remove these from mach-shmobile.

Also select timers per SoC via SYS_SUPPORTS_xxx.
Signed-off-by: NMagnus Damm <damm@opensource.se>
Acked-by: NJohn Stultz <john.stultz@linaro.org>
Signed-off-by: NWolfram Sang <wsa@sang-engineering.com>
Signed-off-by: NDaniel Lezcano <daniel.lezcano@linaro.org>