arm64: Enable RW, RX and RO mappings for the relocated binary

arm64: Enable RW, RX and RO mappings for the relocated binary

Now that we have everything in place switch the page permissions for
.rodata, .text and .data just after we relocate everything in top of the
RAM.

Unfortunately we can't enable this by default, since we have examples of
U-Boot crashing due to invalid access. This usually happens because code
defines const variables that it later writes. So hide it behind a Kconfig
option until we sort it out.

It's worth noting that EFI runtime services are not covered by this
patch on purpose. Since the OS can call SetVirtualAddressMap which can
relocate runtime services, we need to set them to RX initially but remap
them as RWX right before ExitBootServices.

Link: https://lore.kernel.org/u-boot/20250129-rockchip-pinctrl-const-v1-0-450ccdadfa7e@cherry.de/
Link: https://lore.kernel.org/u-boot/20250130133646.2177194-1-andre.przywara@arm.com/
Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>