linux-wandboard

sh: Support userimask for all SH-X3 interrupt controllers.

This shuffles some of the shared bits out of the 7786 code and in to a
shared SH-X3 support file. Presently just for userimask, but also a good
place for the IRQ balancing wrappers.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>