usb: uhci-platform: Make the clock really optional

usb: uhci-platform: Make the clock really optional

Device tree bindings state that the clock is optional for UHCI platform
controllers, and some existing device trees don't provide those - such
as those for VIA/WonderMedia devices.

The driver however fails to probe now if no clock is provided, because
devm_clk_get returns an error pointer in such case.

Switch to devm_clk_get_optional instead, so that it could probe again
on those platforms where no clocks are given.

Cc: stable <stable@kernel.org>
Fixes: 26c502701c52 ("usb: uhci: Add clk support to uhci-platform")
Signed-off-by: Alexey Charkov <alchark@gmail.com>
Link: https://lore.kernel.org/r/20250425-uhci-clock-optional-v1-1-a1d462592f29@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>