regulator: Only update [LDOx|DCx]_HIB_MODE bits in wm8350_[ldo|dcdc]_set_suspend_disable

What we want is to disable output by setting [LDOx|DCx]_HIB_MODE bits.
Current code also clears other bits in LDOx/DCDCx Low Power register.

R202 (CAh) LDO1 Low Power
BIT[13:12] LDO1 Hibernate behaviour:
00 = Select voltage image settings
01 = disable output
10 = reserved
11 = reserved

R182 (B6h) DCDC1 Low Power
BIT[14:12] DC-DC1 Hibernate behaviour:
000 = Use current settings (no change)
001 = Select voltage image settings
010 = Force standby mode
011 = Force standby mode and voltage image settings.
100 = Force LDO mode
101 = Force LDO mode and voltage image settings.
110 = Reserved.
111 = Disable output

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>