s390/pci: add missing EX_TABLE entries to __pcistg_mio_inuser()/__pcilg_mio_inuser()

For some exception types the instruction address points behind the
instruction that caused the exception. Take that into account and add
the missing exception table entry.

Cc: <stable@vger.kernel.org>
Fixes: f058599e ("s390/pci: Fix s390_mmio_read/write with MIO")
Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>