arm64: Add regs_return_value() in syscall.h

This macro, regs_return_value, is used mainly for audit to record system
call's results, but may also be used in test_kprobes.c.

Change-Id: Ia0247b8e62798e11923c4a869e2cc079979109ad
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Git-commit: d34a3ebd8d25cf691a94fae66a957a480cf46430
Git-repo: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git


Signed-off-by: Pratik Patel <pratikp@codeaurora.org>