drivers: pinmux: rv32m1: Convert driver to new DT_INST macros

Convert driver to use DT_INST macros and remove related board per
instance Kconfig symbol usage.

Updated the openisa,rv32m1_vega-pinmux binding to require the label
property and updated the rv32m1.dtsi to add label properties for the
pinmux nodes.

Also update gpio_basic_api test to use DT_NODELABEL.

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>
7 files changed