ARM: OMAP: fix erroneous mmc2 clock change on mmc3 setup

hsmmc23_before_set_reg() can set MMCSDIO2ADPCLKISEL bit, which
enables internal clock for MMC2. Currently this function is also called
by code handling MMC3, and if .internal_clock is set in platform data
(by default it currently is), it will set MMCSDIO2ADPCLKISEL for MMC2
instead of MMC3 (MMC3 doesn't have such bit so nothing actually needs to
be done). This breaks 2nd SD slot on pandora.

Fix this by changing hsmmc23_before_set_reg() to only handle MMC2.
Note that this removes .remux() call for MMC3, but no board currently
needs it and it's also not called for MMC4 and MMC5.

Signed-off-by: Grazvydas Ignotas <notasas@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>