eal/arm: inline 128-bit atomic compare exchange with GCC
eal/arm: inline 128-bit atomic compare exchange with GCC

GCC [1] now assigns even register pairs for CASP, the fix has also been
backported to all stable releases of older GCC versions.
Removing the manual register allocation allows GCC to inline the
functions and pick optimal registers for performing CASP.

1: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=563cc649beaf

Signed-off-by: Pavan Nikhilesh <8184a94f8f7778086ea0697cdb513b2e42813b09@marvell.com>
Acked-by: Ruifeng Wang <a548d51fbc42485a8ba807711a537e88c2b59dd2@arm.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk