mmc: core: do not reinsert prepeared FUA and FLUSH requests in stop flow

When mmc context has unblocked from waiting current request because of
urgent request notification coming from block layer, there is prepeared
request.  In the case, when the request is REQ_FUA or REQ_FLUSH, the
flow should not reinsert it back to i/o scheduler (since according to
block layer logic flush requests with data should never enter elevator).
Instead this request starts immediately.

Change-Id: Ia78b56c6135dd1a8d75a98fd5b771a5035e5c360
Signed-off-by: Konstantin Dorfman <kdorfman@codeaurora.org>
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>
Signed-off-by: edoko <r_data@naver.com>

Change-Id: I8a5021a2fb2936c00ffd456663a76cb1b23e3100