OMAP3+: VC: make I2C config programmable with PMIC-specific settings

Remove hard-coded I2C configuration in favor of settings that can be
configured from PMIC-specific values.  Currently only high-speed mode
and the master-code value are supported, since they were the only
fields currently used, but extending this is now trivial.

Thanks to Nishanth Menon <nm@ti.com> for reporting/fixing a sparse
problem and making omap_vc_i2c_init() static, as well as finding and
fixing a problem with the shift/mask of mcode.

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