soc: intel_adsp: fix linker script for XCC

XCC's linker cannot properly process our linker script with
regard to cached/uncached memory regions as the linker cannot
correctly calculate addresses using boolean operations.
Fix this by doing address pointer arithmetic manually to
move between cached and uncached memory regions.

The addresses of symbols were compared via nm and they are
the same before and after this change.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>