ramfunc region is copied into RAM from FLASH region during XIP init. We
copy from the loadaddr of the region, and were previously loading to the
symbol __ramfunc_start. This is incorrect when using an MPU with
alignment requirements, as the __ramfunc_start symbol may have padding
placed before it in the region. The __ramfunc_start symbol still needs
to be aligned in order to be used by the MPU though, so define a new
symbol __ramfunc_region_start, and use that symbol when copying the
__ramfunc region from FLASH to RAM.
Fixes#75296
Signed-off-by: Daniel DeGrasse <daniel.degrasse@nxp.com>