scsi: dt-bindings: ufs: Remove custom property "<name>-fixed-regulator"

Custom device tree property "<name>-fixed-regulator" can be removed
because,

1) It is not used anywhere in tree.

2) All handlings for "<name>-fixed-regulator" have been removed in UFS
   driver.

3) There is no issue if an existed regulator defined
   "<name>-fixed-regulator" property in device tree.
Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt

@@ -31,7 +31,6 @@ Optional properties:
 - vcc-max-microamp      : specifies max. load that can be drawn from vcc supply
 - vccq-max-microamp     : specifies max. load that can be drawn from vccq supply
 - vccq2-max-microamp    : specifies max. load that can be drawn from vccq2 supply
-- <name>-fixed-regulator : boolean property specifying that <name>-supply is a fixed regulator
 
 - clocks                : List of phandle and clock specifier pairs
 - clock-names           : List of clock input name strings sorted in the same
@@ -63,7 +62,6 @@ Example:
 		interrupts = <0 28 0>;
 
 		vdd-hba-supply = <&xxx_reg0>;
-		vdd-hba-fixed-regulator;
 		vcc-supply = <&xxx_reg1>;
 		vcc-supply-1p8;
 		vccq-supply = <&xxx_reg2>;