powerpc: Merge atomic.h and memory.h into powerpc

Merged atomic.h into include/powerpc.  Moved asm-style HMT_ defines from
memory.h into ppc_asm.h, where there were already HMT_defines; moved c-style
HMT_ defines to processor.h. Renamed memory.h to synch.h to better reflect
its contents.
Signed-off-by: NKumar Gala <kumar.gala@freescale.com>
Signed-off-by: NBecky Bruce <becky.bruce@freescale.com>
Signed-off-by: NJon Loeliger <linuxppc@jdl.com>
Signed-off-by: NPaul Mackerras <paulus@samba.org>