ARM: dts: am57xx-beagle-x15: mmc1: remove redundant pbias-supply property

pbias-supply is initialized in dra7.dtsi. Remove redundant initialization
of pbias-supply from MMC1 dt node in am57xx-beagle-x15.dts
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/boot/dts/am57xx-beagle-x15.dts

@@ -580,7 +580,6 @@ &mmc1 {
 
 	vmmc-supply = <&ldo1_reg>;
 	vmmc_aux-supply = <&vdd_3v3>;
-	pbias-supply = <&pbias_mmc_reg>;
 	bus-width = <4>;
 	cd-gpios = <&gpio6 27 0>; /* gpio 219 */
 };