pinctrl: rv32m1: delay init priority after the clock controller

The rv32m1 pinctrl driver depends on clock controller, add a new symbol
and set it so it gets initialized after that, and before other devices.

Fixes:

$ west build -p -b rv32m1_vega_ri5cy tests/kernel/common \
		-DCONFIG_CHECK_INIT_PRIORITIES=y
...
ERROR: /soc/pinmux@41037000 PRE_KERNEL_1 1 < \
		/soc/clock-controller@41027000 PRE_KERNEL_1 30

Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>