split-path: CALL_EXPR can't show up in gimple_assign

While working on split path, I noticed that poor_ifcvt_candidate_code
would check for CALL_EXPR but that can't show up in gimple_assign
so this removes that check.

This could be a very very small compile time improvement.

Bootstrapped and tested on x86_64-linux-gnu.

gcc/ChangeLog:

	* gimple-ssa-split-paths.cc (poor_ifcvt_candidate_code): Remove CALL_EXPR handling.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>