OMAP3+: VC: cleanup voltage setup time configuration

- add setup_time field to struct omap_vc_channel (init'd from PMIC data)
- use VC/VP register access helper for read/modify/write
- move VFSM structure from omap_vdd_info into struct voltagedomain
- remove redunant _data suffix from VFSM structures and variables
- remove voltsetup_shift, use ffs() on the mask value to find the shift

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