[MMC] Explain the internals of mmc_power_up()
[MMC] Explain the internals of mmc_power_up()

It seems that people get confused about what is happening in
mmc_power_up().  Add a comment to make it clear why we have
a two stage process.

Signed-off-by: Russell King <f6aa0246ff943bfa8602cdf60d40c481b38ed232@arm.linux.org.uk>

TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs