mmc: tmio_mmc: Move some defines into a shared header

Also add TMIO_BBS.

This allows these defines to also be used by zboot.

Cc: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Chris Ball <cjb@laptop.org>