pmdomain: bcm: bcm2835-power: Use devm_clk_get_optional

pmdomain: bcm: bcm2835-power: Use devm_clk_get_optional

The driver tries to implement optional clock handling with devm_clk_get.
It treats all errors except EPROBE_DEFER as a missing clock, which is
not correct. So use devm_clk_get_optional here and get the corner-cases
right.

Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://lore.kernel.org/r/20250415190558.16354-1-wahrenst@gmx.net
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>