omap: RX51: Remux to pull eMMC lines down when powering off

It has been discovered that, when eMMC is powered off, current
will flow from OMAP eMMC data pull-ups to the eMMC voltage supply.
Configuring pads for OMAP off-mode does not help because eMMC is
powered off independently of OMAP off-mode.  Hence the pads are
now re-configured when eMMC is powered on or off.

Signed-off-by: Adrian Hunter <adrian.hunter@nokia.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>