parisc: Fix HPMC handler by increasing size to multiple of 16 bytes

Make sure that the HPMC (High Priority Machine Check) handler is 16-byte
aligned and that it's length in the IVT is a multiple of 16 bytes.
Otherwise PDC may decide not to call the HPMC crash handler.

Signed-off-by: Helge Deller <deller@gmx.de>
Cc: stable@vger.kernel.org