arm64: trans_pgd: pass allocator trans_pgd_create_copy

Make trans_pgd_create_copy and its subroutines to use allocator that is
passed as an argument

Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: James Morse <james.morse@arm.com>
Link: https://lore.kernel.org/r/20210125191923.1060122-6-pasha.tatashin@soleen.com
Signed-off-by: Will Deacon <will@kernel.org>