scsi: ufs: Remove "<name>-fixed-regulator" device tree property

scsi: ufs: Remove "<name>-fixed-regulator" device tree property

"<name>-fixed-regulator" device tree property can be safely removed because
below things are fixed or resolved,

1. "<name>-max-microamp" becomes optional property: Undefined
   "<name>-max-microamp" will not cause initialization fail if
   "<name>-fixed-regulator" is not defined.

2. Current switching operation (by regulator_set_load) now has rules:
   Regulators will have undefined current limit if "<name>-fixed-regulator"
   is not defined. But this is safe because only regulator which has
   configured current limit from "<name>-max-microamp" property is allowed
   to change its load.

Although "<name>-fixed-regulator" is not used in any dt-bindings in tree,
this patch is still safe for regulators already defined
"<name>-fixed-regulator". To be more clear, if a regulator defined
"<name>-fixed-regulator" before, the behavior difference after this patch
is,

1. "<name>-max-microamp":
   If a regulator defined "<name>-fixed-regulator", it is not necessary
   to define "<name>-max-microamp" property in device tree and it is
   expected to have an undefined current limit, i.e., "max_uA" field
   is zero in struct ufs_vreg. This is exactly the same as patched.

2. "vcc-supply-1p8" or volatge range settings:
   * For vcc, vccq or vccq2, these three regulators shall not define
     "<name>-fixed-regulator" because defining it will lead to
     undefined voltage range and thus voltage switching will be
     unexpected.
   * For other regulators with undefined voltage range, voltage range
     will be still undefined after patched.

Therefore this patch is safe for all existed regulators with
"<name>-fixed-regulator" property already defined.

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>