mmc: bcm2835: Introduce proper clock handling

mmc: bcm2835: Introduce proper clock handling

The custom sdhost controller on BCM2835 is feed by the critical VPU clock.
In preparation for PM suspend/resume support, add a proper clock handling
to the driver like in the other clock consumers (e.g. I2C).

Move the clock handling behind mmc_of_parse(), because it could return
with -EPROBE_DEFER and we want to minimize potential clock operation during
boot phase.

Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
Message-ID: <20241025103621.4780-5-wahrenst@gmx.net>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>