Match: Add interface match_cond_with_binary_phi for true/false arg

When matching the cond with 2 args phi node, we need to figure out
which arg of phi node comes from the true edge of cond block, as
well as the false edge.  This patch would like to add interface
to perform the action and return the true and false arg in TREE type.

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

gcc/ChangeLog:

	* gimple-match-head.cc (match_cond_with_binary_phi): Add new func
	impl to match binary phi for true and false arg.

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