reset: sti: allow building under COMPILE_TEST

The STIH407 reset driver can be compiled without ARCH_STI being
enabled. Allow it to be built under COMPILE_TEST.

Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
Link: https://lore.kernel.org/r/20240621-reset-compile-sti-v1-1-b7a66ce29911@pengutronix.de


Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>