OMAP3+: VP: struct omap_vp_common: replace shift with __ffs(mask)

In struct omap_vp_common, the shift value can be derived from the mask
value by using __ffs(), so remove the shift value for the various
VPCONFIG bitfields, and use __ffs() in the code for the shift value.

While here, rename field names in kerneldoc comment to match actual
field names in structure.  Also, cleanup indendentaion for other VP
register accesses in omap_vp_init().

No functional changes.

Signed-off-by: Kevin Hilman <khilman@ti.com>