arm64: dts: adapt to LP855X bindings changes

Change underscores in ROM node names to dashes, and remove deprecated
pwm-period property.
Signed-off-by: Artur Weber <aweber.kernel@gmail.com>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230519180728.2281-5-aweber.kernel@gmail.com

arch/arm64/boot/dts/nvidia/tegra210-p2371-2180.dts

@@ -58,19 +58,17 @@ backlight: backlight@2c {
 			dev-ctrl = /bits/ 8 <0x80>;
 			init-brt = /bits/ 8 <0xff>;
 
-			pwm-period = <29334>;
-
 			pwms = <&pwm 0 29334>;
 			pwm-names = "lp8557";
 
 			/* boost frequency 1 MHz */
-			rom_13h {
+			rom-13h {
 				rom-addr = /bits/ 8 <0x13>;
 				rom-val = /bits/ 8 <0x01>;
 			};
 
 			/* 3 LED string */
-			rom_14h {
+			rom-14h {
 				rom-addr = /bits/ 8 <0x14>;
 				rom-val = /bits/ 8 <0x87>;
 			};