The ARC EM family processors do not support native atomic assembly
instructions (LLOCK and SCOND). Therefore, the assembly version
of atomic functions cannot be used. This adds pure C version of
these atomic functions.
Change-Id: Ic64dd31b0367b6dcf3a46f41c0c7ac2c2ce5eb8d
Signed-off-by: Daniel Leung <daniel.leung@intel.com>