MN10300: Specify an ELF HWCAP flag for MN10300 Atomic Operations Unit support

Use an ELF HWCAP flag to indicate to the process that the CPU provides LL/SC
equivalent atomic operations unit support in addition to BSET/BCLR.

Signed-off-by: Mark Salter <msalter@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>