s390/extable: add EX_TABLE_UA_LOAD_REGPAIR() macro

Add new exception table type which is able to handle register
pairs. If an exception is recognized on such an instruction the
specified register pair will be zeroed, and the specified error
register will be modified so it contains -EFAULT, similar to the
existing EX_TABLE_UA_LOAD_REG() macro.

Link: https://lore.kernel.org/r/Y2J8RSW2khWLgpPo@osiris


Signed-off-by: Heiko Carstens <hca@linux.ibm.com>