omap3: igep3: Fix IGEP module second MMC channel power supply

The second MMC channel (used by the WLAN/BT module) is not linked to
power regulator. This causes the WLAN/BT module to fail being detected if
CONFIG_REGULATOR_DUMMY is not set.

This patch adds the two regulators that actually feed the WLAN/BT module
(1v8 from the TWL4030 VIO LDO, and a fixed 3v3). With that patch, the
second channel is properly detected.

Also change vmmc1 to use symbolic names instead of direct device
reference.

Signed-off-by: Enric Balletbo i Serra <eballetbo@gmail.com>
Acked-by: Marc Zyngier <maz@misterjones.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>