Genmatch: Fix ICE for binary phi cfg mismatching [PR116795]

This patch would like to fix one ICE when try to match the binary
phi for below cfg.  We check the first edge of the Phi block comes
from b0, instead of check the only one edge of b1 comes from the
b0 too.  Thus, it will result in some code to be recog as .SAT_SUB
but it is not, and finally result the verify_ssa failure.

+------+
| b0:  |
| def  |       +-----+
| ...  |       | b1: |
| cond |------>| def |
+------+       | ... |
   |           +-----+
   |              |
   |              |
   v              |
+-----+           |
| b2: |           |
| Phi |<----------+
+-----+

The below test suites are passed for this patch.
* The rv64gcv fully regression test.
* The x86 bootstrap test.
* The x86 fully regression test.

	PR target/116795

gcc/ChangeLog:

	* gimple-match-head.cc (match_cond_with_binary_phi): Fix the
	incorrect cfg check as b0->b1 in above example.

gcc/testsuite/ChangeLog:

	* gcc.dg/torture/pr116795-1.c: New test.

Signed-off-by: Pan Li <pan2.li@intel.com>