arm: asm: relaxed.h: defined relaxed.h

Defined a new header file relaxed.h, which uses generic
definitions of some macros used by arm64 for improving
power efficiency.

bug 1440421

Signed-off-by: Sumit Singh <sumsingh@nvidia.com>
Reviewed-on: http://git-master/r/398766
(cherry picked from commit a96e59b1959f3ee216503b4f9df3cb75f7093ed6)
Reviewed-on: http://git-master/r/422211
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Bharat Nihalani <bnihalani@nvidia.com>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>