arm64: dts: meson-sm1: Fix the pwm regulator supply properties

After enabling CONFIG_REGULATOR_DEBUG=y we observe below debug logs.
Changes help link VDDCPU pwm regulator to 12V regulator supply
instead of dummy regulator.

[   11.602281] pwm-regulator regulator-vddcpu: Looking up pwm-supply property
               in node /regulator-vddcpu failed
[   11.602344] VDDCPU: supplied by regulator-dummy
[   11.602365] regulator-dummy: could not add device link regulator.11: -ENOENT
[   11.602548] VDDCPU: 721 <--> 1022 mV at 1022 mV, enabled

Fixes: 88d537bc ("arm64: dts: meson: convert meson-sm1-odroid-c4 to dtsi")
Fixes: 700ab8d8 ("arm64: dts: khadas-vim3: add support for the SM1 based VIM3L")
Fixes: 3d9e7648 ("arm64: dts: meson-sm1-sei610: enable DVFS")
Fixes: 976e9201 ("arm64: dts: meson-sm1: add Banana PI BPI-M5 board dts")

Cc: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Anand Moon <linux.amoon@gmail.com>
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://lore.kernel.org/r/20210919202918.3556-4-linux.amoon@gmail.com