[BSW/BDW] skia lcdblendmode & lcdoverlap test failure

2 skia test gles_lcdblendmode & gles_lcdoverlap fails only in brw/bdw , skl+ works fine.

Image rendered has missing text portion or some extra lines and dots (refer attached image src text)

correct image

This happens only for text rendered with blend mode SkBlendMode::kSrc (Replaces destination with source. Destination alpha and color component values are ignored.) all other blend mode works fine

If dri config "always_flush_cache" is set true then these issue is not observed

test lcdblendmode : https://skia.googlesource.com/skia/+/refs/heads/master/gm/lcdblendmodes.cpp