regulator: fan53555: fix TCS4525 voltage calulation

regulator: fan53555: fix TCS4525 voltage calulation

The TCS4525 has 128 voltage steps. With the calculation set to 127 the
most significant bit is disregarded which leads to a miscalculation of
the voltage by about 200mv.

Fix the calculation to end deadlock on the rk3566-quartz64 which uses
this as the cpu regulator.

Fixes: 8bb049182cdd ("regulator: fan53555: Add TCS4525 DCDC support")
Signed-off-by: Peter Geis <pgwipeout@gmail.com>
Link: https://lore.kernel.org/r/20210511211335.2935163-2-pgwipeout@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>