mfd: Correct WM835x ISINK ramp time defines

The constants used to specify ISINK ramp times for WM835x had the
wrong shifts so that the on times applied to the off ramp and vice
versa. The masks for the bitfields are correct.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: stable@kernel.org
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>