omap_hsmmc: Allow for a shared VccQ

EMMC can have two voltage supplies, Vcc and VccQ
which are implemented in the code as consumer
supplies vmmc and vmmc_aux.

If the regulator that supplies vmmc_aux is shared
with other consumers, then sending it to sleep
will disrupt those consumers.  However, the
TWL4030-family regulators may have OFF remapped
to SLEEP, in which case 'regulator_disable()'
will put the regulator to sleep only when all
consumers are disabled - which is the desired
behaviour.

This patch adds a platform data field to allow
that option.

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