The swpb in macro MUTEX_SET will cause "undefined instruction" error
on the new arm arches which don't support this assembly instruction
any more. If use ldrex/strex to replace swpb, the old arm arches don't
support them. So to avoid this issue, just disable the ARM assembler
mutex code, and use the default pthreads mutex.
Signed-off-by: Li Zhou <li.zhou@windriver.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
