scsi: ufs: Fix regulator load and icc-level configuration

Currently if a regulator has "<name>-fixed-regulator" property in device
tree, it will skip current limit initialization.  This lead to a zero
"max_uA" value in struct ufs_vreg.

However, "regulator_set_load" operation shall be required on regulators
which have valid current limits, otherwise a zero "max_uA" set by
"regulator_set_load" may cause unexpected behavior when this regulator is
enabled or set as high power mode.

Similarly, in device's icc_level configuration flow, the target icc_level
shall be updated if regulator also has valid current limit, otherwise a
wrong icc_level will be calculated by zero "max_uA" and thus causes
unexpected results after it is written to device.

Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
Reviewed-by: Avri Altman <avri.altman@wdc.com>
Acked-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>