ARM: dts: am33xx-clocks: Fix ehrpwm tbclk data on am33xx

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: 9e100ebafb91: ("Fix ehrpwm tbclk data")
Signed-off-by: Vignesh R <[e-mail]>
Acked-by: Tero Kristo <[e-mail]>
Signed-off-by: Tony Lindgren <[e-mail]>

arch/arm/boot/dts/am33xx-clocks.dtsi

···
 	ehrpwm0_tbclk: ehrpwm0_tbclk@44e10664 {
 		#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@44e10664 {
 		#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@44e10664 {
 		#clock-cells = <0>;
 		compatible = "ti,gate-clock";
-		clocks = <&dpll_per_m2_ck>;
+		clocks = <&l4ls_gclk>;
 		ti,bit-shift = <2>;
 		reg = <0x0664>;
 	};