arm64: arm: Fix-up the removal of the arm64 regs_query_register_name() prototype

Commit 0a8ea52c ("arm64: Add HAVE_REGS_AND_STACK_ACCESS_API
feature") inadvertently removed the arch/arm prototype instead of the
arm64 one introduced by the original patch. There should not be any
bisection issues since this function is not called from anywhere else
(it could as well be removed from arch/arm at some point).

Fixes: 0a8ea52c

 ("arm64: Add HAVE_REGS_AND_STACK_ACCESS_API feature")
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>