ARM: dts: omap3-beagle: Fix USB host on beagle boards (for 3.13)

Beagle (rev. C4) and Beagle-XM (all revs) need VAUX2 1.8V supply
for the USB PHY.

As the generic PHY driver can't handle more than one supply
at the moment, we configure this supply to be always on.
This will cause a very small power impact if the USB host subsystem
is not in use, about 76.86 micro-W + LDO power.

Older Beagle boards (prior to C4) don't have VAUX2 connected anywhere,
so there won't be any functional impact on those boards other than
some additional LDO power consumption.

Reported-by: Nishanth Menon <nm@ti.com>
Tested-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>