soc: infineon: edge: Correct initialization of MPU regions and linker fix

Now that the cores have dedicated executable regions
for the code relocation, give executable permissions only
to those rather than the entire RAM region.
Additionally, removed the rwdata exception for the assembly
file given that it now gets properly placed in the correct region
by the relocate script.

Signed-off-by: Laura Carlesso <laura.carlesso@infineon.com>