timer: optimize apply_slack()

__fls(mask) is equivalent to find_last_bit(&mask, BITS_PER_LONG), but cheaper.
find_last_bit was showing up high on the list when I was profiling for stalls
on icache misses on a system with very small cache size (MIPS).

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
 drivers: mmc: disable CRC.
taken from https://github.com/franciscofranco/mako/commit/010cc8a7c3a25592f66089e10be701f4f3d9bfc8
Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
Squashed update of kernel from 3.0.69 to 3.0.70