material.cpp speedup

When checking for very few or no pawns for scale factor, if there are no pawns don't check for one pawn.
Bench results below:

Base	speed
4047	3994
4078	4030
4055	4001
4016	3985
4047	4016
4063	4031
	
Averages	
4051	4010
	
+1.0% Speed up	
No functional change