arm64: Add a macro to find a VM fault address

Add a macro to find which bits from far_el2 are needed to be copied
to get the full intermediate physical address (IPA).

The hpfar_el2 register only contains a 4k aligned fault address. We
need to include the lower bits from far_el2 if we need the full
faulting IPA.

(cherry picked from commit b3bbec37ba039a46f7166f6fa3571f38da4253e9)