sh: Fix exception_handling_table alignment.

With the recent change ripping out interrupt_table, explicit
padding of the table was missing, causing bad things to happen
when manually inserting handlers in to the table. This problem
particularly showed up in relation to do_fpu_state_restore()
which was inserted quite deeply in to the table and ended up
scribbling over a slab object.

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