OMAP3+: PM: VC: handle mutant channel config for OMAP4 MPU channel

On OMAP3+, all VC channels have the the same bitfield ordering for all
VC channels, except the OMAP4 MPU channel.  This appears to be a freak
accident as all other VC channel (including OMAP5) have the standard
configuration.  Handle the mutant case by adding a per-channel flag
to signal the deformity and handle it during VC init.

Special thanks to Nishanth Menon <nm@ti.com> for finding this problem
and for proposing the initial solution.

Cc: Nishanth Menon <nm@ti.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>