arm64: dts: qcom: pm8350c: Drop PWM reg declaration

The PWM is a part of the SPMI PMIC block and maps several different
addresses within the SPMI block. It is not accurate to describe as pwm@reg
as a result.

Fixes: 5be66d2d ("arm64: dts: qcom: pm8350c: Add pwm support")
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>