fate: Explicitly specify the pixel format for the pngparser test

The RGB32 pixel format is RGBA/BGRA depending on target
endianness - make sure to convert it to one specific format for
the framecrc tests.

This fixes the pngparser fate test on big endian.
Signed-off-by: Martin Storsjö <martin@martin.st>

tests/fate/image.mak

@@ -5,7 +5,7 @@ FATE_SAMPLES_AVCONV-$(call DEMDEC, IMAGE2, PICTOR) += fate-pictor
 fate-pictor: CMD = framecrc -i $(TARGET_SAMPLES)/pictor/MFISH.PIC -pix_fmt rgb24
 
 FATE_SAMPLES_AVCONV-$(call PARSERDEMDEC, PNG, IMAGE2PIPE, PNG) += fate-pngparser
-fate-pngparser: CMD = framecrc -f image2pipe -i $(TARGET_SAMPLES)/png1/libav_4x_concat.png
+fate-pngparser: CMD = framecrc -f image2pipe -i $(TARGET_SAMPLES)/png1/libav_4x_concat.png -pix_fmt rgba
 
 FATE_SAMPLES_AVCONV-$(call DEMDEC, IMAGE2, PTX) += fate-ptx
 fate-ptx: CMD = framecrc -i $(TARGET_SAMPLES)/ptx/_113kw_pic.ptx -pix_fmt rgb24