OMAP5: SR: support reading VC registers on ES2.0

ES2.0 currently displays 0 when omapconf show sr is invoked.
This is because of the register differences between ES1.0 and 2.0.

Handle that on the fly.

Signed-off-by: Nishanth Menon <nm@ti.com>
Merge pull request #14 from nmenon/o5-sr-vc-fix

OMAP5: SR: support reading VC registers on ES2.0