arm64: lib: use pair accessors for copy_*_user routines

The AArch64 instruction set contains load/store pair memory accessors,
so use these in our copy_*_user routines to transfer 16 bytes per
iteration.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --cc arch/arm64/lib/copy_from_user.S
Simple merge

diff --cc arch/arm64/lib/copy_in_user.S
Simple merge

diff --cc arch/arm64/lib/copy_to_user.S
Simple merge