sh: intc - remove default interrupt priority tables

This patch removes interrupt priority tables from the intc code.
Optimal priority assignment varies with embedded application anyway,
so keeping the interrupt priority tables together with cpu-specific
code doesn't make sense.

The function intc_set_priority() should be used instead to set the
desired interrupt priority level.

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