Enable MMC_UNSAFE_RESUME to accomplish a proper suspend/resume cycle
for SD/SDIO/(e)MMC.
ARMMMCI host driver supports clock gating through runtime PM, thus
MMC_CLKGATE is not needed. Moreover ARMMMCI can do scatter-gather which
means we can explicity disable MMC_BLOCK_BOUNCE, since it's default
enabled, to skip unnecessary bounce buffer copying.