mmc: cb710: partially demystify clock selection
mmc: cb710: partially demystify clock selection

Clock divider selection in partially verified, so document known facts
in code.

Signed-off-by: Michał Mirosław <a6cdb63bb4a601d03a6f05cfd687541da1200a64@rere.qmqm.pl>
Signed-off-by: Chris Ball <6ca7faee6ca9a094b1ee341f11b840a5608a8746@laptop.org>

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