regulator: max77802: Add set suspend mode for BUCKs and simplify code

regulator: max77802: Add set suspend mode for BUCKs and simplify code

The max77802 PMIC has a special enable pin (PWRREQ) that can be used
by the Application Processor (AP) to power down and up voltage rails.

The max77802 PMIC regulators have 3 different enable control logics.
Some regulators support to be configured on different operational mode
during normal operation while others only support to be put in a Low
Power Mode while the system has entered in sleep mode. Some regulators
don't even support that configuration. The logics are the following:

Enable Control Logic1 by PWRREQ (BUCK 2-4, LDO2, LDO4-19, LDO22, LDO35)
-------------------------------
0: Output OFF
1: Output ON/OFF (Controlled by PWRREQ)
     PWRREQ = HIGH (1): Output ON in Normal Mode
     PWRREQ = LOW (0): Output OFF
2: Output On with Low Power Mode (Controlled by PWRREQ)
     PWRREQ = HIGH (1) : Output ON in Normal Mode
     PWRREQ = LOW (0): Output ON in Low Power Mode
3: Output ON in Normal Mode

Enable Control Logic2 by PWRREQ (LDO1, LDO20, LDO21)
-------------------------------
0: Output ON/OFF by ENx
1: Output ON in Low Power Mode
2: Output ON in Low Power Mode (Controlled by PWRREQ)
   PWRREQ = HIGH (1): Output ON in Normal Mode
   PWRREQ = LOW (0): Output ON in Low Power Mode
3: Output ON in Normal Mode

Enable Control Logic3 by PWRREQ (LDO3)
-------------------------------
0 or 3: Output ON in Normal Mode
1: Output ON in Low Power Mode
2: Output ON in Low Power Mode (Controlled by PWRREQ)
   PWRREQ = HIGH (1): Output ON in Normal Mode
   PWRREQ = LOW (0): Output ON in Low Power Mode

The driver only implemented .set_suspend_mode for the LDOs regulators
but some BUCKs also support to be put in Low Power Mode on system wide
suspend so they should be supported as well. Two different functions
were used for the logic 1 and 2 but this is not necessary.

Only normal and Low Power Mode are valid operational modes, OFF is not
an mode but is a regulator state that is handled by .set_suspend_enable
ad .set_suspend_disable. So the same .set_suspend_mode function can be
used by all the regulators that support Output On with Low Power Mode
by PWRREQ, making much simpler the code to set the suspend mode.

Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: Mark Brown <broonie@kernel.org>