xen/arm: Use the newly introduced MFN <-> MADDR and GFN <-> MADDR helpers

xen/arm: Use the newly introduced MFN <-> MADDR and GFN <-> MADDR helpers

Replace the following constructions:
    - _gfn(paddr_to_pfn(...))   => gaddr_to_gfn(...)
    - _mfn(paddr_to_pfn(...))   => maddr_to_mfn(...)
    - pfn_to_paddr(mfn_x(...))  => mfn_to_maddr(...)
    - pfn_to_paddr(gfn_x(...))  => gfn_to_gaddr(...)
    - _mfn(... >> PAGE_SHIFT)   => maddr_to_mfn(...)

Signed-off-by: Julien Grall <julien.grall@arm.com>
Acked-by: Tamas K Lengyel <tamas@tklengyel.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Cc: Razvan Cojocaru <rcojocaru@bitdefender.com>
Cc: Tamas K Lengyel <tamas@tklengyel.com>