Merge common code between Sparc, PowerPC and Microblaze.

Sparc differs in the implementation at this point, so this patch uses
a #ifdef to handle sparc differently for now.  The merging of
implementations will occur in a later patch
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>
Acked-by: NDavid S. Miller <davem@davemloft.net>
Acked-by: NWolfram Sang <w.sang@pengutronix.de>
Acked-by: NMichal Simek <monstr@monstr.eu>
Acked-by: NStephen Neuendorffer <stephen.neuendorffer@xilinx.com>
Acked-by: NStephen Rothwell <sfr@canb.auug.org.au>