sh: mach-se: Convert SE7343 FPGA to dynamic IRQ allocation.

This gets rid of the arbitrary set of vectors used by the SE7722 FPGA
interrupt controller and switches over to a completely dynamic set.
No assumptions regarding a contiguous range are made, and the platform
resources themselves need to be filled in lazily.

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