ARM: dts: am43xx-clocks: Fix ehrpwm tbclk data on am43xx

ehrpwm tbclk is wrongly modelled as deriving from dpll_per_m2_ck.
The TRM says tbclk is derived from SYSCLKOUT. SYSCLKOUT nothing but the
functional clock of pwmss (l4ls_gclk).
Fix this by changing source of ehrpwmx_tbclk to l4ls_gclk.

Fixes: 4da1c67719f61 ("add tbclk data for ehrpwm")
Signed-off-by: Vignesh R <[e-mail]>
Acked-by: Tero Kristo <[e-mail]>
Signed-off-by: Tony Lindgren <[e-mail]>

arch/arm/boot/dts/am43xx-clocks.dtsi

···
 	ehrpwm0_tbclk: ehrpwm0_tbclk {
 		#clock-cells = <0>;
 		compatible = "ti,gate-clock";
-		clocks = <&dpll_per_m2_ck>;
+		clocks = <&l4ls_gclk>;
 		ti,bit-shift = <0>;
 		reg = <0x0664>;
 	};
···
 	ehrpwm1_tbclk: ehrpwm1_tbclk {
 		#clock-cells = <0>;
 		compatible = "ti,gate-clock";
-		clocks = <&dpll_per_m2_ck>;
+		clocks = <&l4ls_gclk>;
 		ti,bit-shift = <1>;
 		reg = <0x0664>;
 	};
···
 	ehrpwm2_tbclk: ehrpwm2_tbclk {
 		#clock-cells = <0>;
 		compatible = "ti,gate-clock";
-		clocks = <&dpll_per_m2_ck>;
+		clocks = <&l4ls_gclk>;
 		ti,bit-shift = <2>;
 		reg = <0x0664>;
 	};
···
 	ehrpwm3_tbclk: ehrpwm3_tbclk {
 		#clock-cells = <0>;
 		compatible = "ti,gate-clock";
-		clocks = <&dpll_per_m2_ck>;
+		clocks = <&l4ls_gclk>;
 		ti,bit-shift = <4>;
 		reg = <0x0664>;
 	};
···
 	ehrpwm4_tbclk: ehrpwm4_tbclk {
 		#clock-cells = <0>;
 		compatible = "ti,gate-clock";
-		clocks = <&dpll_per_m2_ck>;
+		clocks = <&l4ls_gclk>;
 		ti,bit-shift = <5>;
 		reg = <0x0664>;
 	};
···
 	ehrpwm5_tbclk: ehrpwm5_tbclk {
 		#clock-cells = <0>;
 		compatible = "ti,gate-clock";
-		clocks = <&dpll_per_m2_ck>;
+		clocks = <&l4ls_gclk>;
 		ti,bit-shift = <6>;
 		reg = <0x0664>;
 	};