pmdomain: airoha: Fix compilation error with Clang-20 and Thumb2 mode

pmdomain: airoha: Fix compilation error with Clang-20 and Thumb2 mode

The use of R7 in the SMCCC conflicts with the compiler's use of R7 as a frame
pointer in Thumb2 mode, which is forcibly enabled by Clang when profiling
hooks are inserted via the -pg switch.

This is a known issue and similar driver workaround this with a Makefile
ifdef. Exact workaround are applied in
drivers/firmware/arm_scmi/transports/Makefile and other similar driver.

Suggested-by: Sudeep Holla <sudeep.holla@arm.com>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202501201840.XmpHXpQ4-lkp@intel.com/
Fixes: 82e703dd438b ("pmdomain: airoha: Add Airoha CPU PM Domain support")
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Link: https://lore.kernel.org/r/20250120153817.11807-1-ansuelsmth@gmail.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>