sh: add romimage-macros.h

romimage macros which are used in kfr2r09 is very useful for other board.
This patch divides kfr2r09's romimage.h into
romimage-macros and partner-jet-setup.

Signed-off-by: Kuninori Morimoto <morimoto.kuninori@renesas.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>