Some architectures (like powerpc) provide status information on the exact
type of invalid exception.  This is pretty straight forward as we already
report invalid exceptions via FP_SET_EXCEPTION.

We add new flags (FP_EX_INVALID_*) the architecture code can define if it
wants the exact invalid exception reported.

We had to split out the INF/INF and 0/0 cases for divide to allow reporting
the two invalid forms properly.
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Acked-by: David S. Miller <davem@davemloft.net>