arch: arm64: mmu: Add zephyr execution regions

Add zephyr execution regions(text, rodata, data, noinit, bss, etc.)
with proper attributes to translation tables.
Linker script has been modified a little to align these sections to
minimum translation granule(4 kB).

With this in place, code cannot be overwritten accidently as it is
marked read only. Similarly, execution is prohibited from data/RW
section as it is marked execute-never.

Signed-off-by: Abhishek Shah <abhishek.shah@broadcom.com>