use fmaxf to prevent casting from and to double

Summary:
Use ```fmaxf``` to prevent double casting.
Closes https://github.com/facebook/css-layout/pull/251

Reviewed By: emilsjolander

Differential Revision: D4199342

Pulled By: splhack

fbshipit-source-id: c04bc68a3c9c97b92e910e885457cf2fe00da28b

CSSLayout/CSSLayout.c

@@ -1812,7 +1812,7 @@ static void layoutNodeImpl(const CSSNodeRef node,
     if (measureModeMainDim == CSSMeasureModeAtMost && remainingFreeSpace > 0) {
       if (!CSSValueIsUndefined(node->style.minDimensions[dim[mainAxis]]) &&
           node->style.minDimensions[dim[mainAxis]] >= 0) {
-        remainingFreeSpace = fmax(0,
+        remainingFreeSpace = fmaxf(0,
                                   node->style.minDimensions[dim[mainAxis]] -
                                       (availableInnerMainDim - remainingFreeSpace));
       } else {