sh: intc - rework core code

This patch reworks the intc core, implementing the following features:

- Support dual priority registers - one set and one clear register
- All 8/16/32 bit register combinations are now supported
- Both single mask and single enable bitmap register are supported
- Add code to set interrupt priority
- Speedup sense and priority configuration code
- Allocate data using bootmem, allows intc data structures to be
  __initdata
- Save memory - allocated memory footprint is smaller than intc
  structures

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>