As there is no need for a Prekernel on aarch64, the Prekernel code was
moved into Kernel itself. The functionality remains the same.
SERENITY_KERNEL_AND_INITRD in run.sh specifies a kernel and an inital
ramdisk to be used by the emulator. This is needed because aarch64
does not need a Prekernel and the other ones do.
Creating pointers from arbitrary values is not a valid thing to do in
constexpr functions. Furthermore, this functions is always called with
runtime values anyways, so there's no use in having it be constexpr.
Instead, make it ALWAYS_INLINE.
