dts64: mt7622: enable all pwm

http://forum.banana-pi.org/t/bpi-r64-pwm-support/11140/13

based on
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/drivers/pinctrl/mediatek/pinctrl-mt7622.c?h=linux-5.4.y#n401

pwm1 (pins 9+11 on gpio-header on bpi-r64):

cd /sys/class/pwm/pwmchip0
echo "0" > export
cd pwm0
echo 10000 > period
echo 5000 > duty_cycle    #half brightness
echo 1 > enable
echo 1000 > duty_cycle    #darker ~ 1/10

mt7622 only supports 6 pwm-channels so drop pwm7

arch/arm64/boot/dts/mediatek/mt7622-bananapi-bpi-r64.dts

@@ -414,10 +414,15 @@
 		};
 	};
 
-	pwm7_pins: pwm1-2-pins {
+	pwm_pins: pwm-pins {
 		mux {
 			function = "pwm";
-			groups = "pwm_ch7_2";
+			groups = "pwm_ch1_0", /* mt7622_pwm_ch1_0_pins[] = { 51, }; */
+				 "pwm_ch2_0", /* mt7622_pwm_ch2_0_pins[] = { 52, }; */
+				 "pwm_ch3_2", /* mt7622_pwm_ch3_2_pins[] = { 97, }; */
+				 "pwm_ch4_1", /* mt7622_pwm_ch4_1_pins[] = { 67, }; */
+				 "pwm_ch5_0", /* mt7622_pwm_ch5_0_pins[] = { 68, }; */
+				 "pwm_ch6_0"; /* mt7622_pwm_ch6_0_pins[] = { 69, }; */
 		};
 	};
 
@@ -537,7 +542,7 @@
 
 &pwm {
 	pinctrl-names = "default";
-	pinctrl-0 = <&pwm7_pins>;
+	pinctrl-0 = <&pwm_pins>;
 	status = "okay";
 };