dri3: Fix pixmap buf_id computation
dri3: Fix pixmap buf_id computation

Looks like some kind of rebase damage to me...

Signed-off-by: Keith Packard <fd7f967895e9f35e58ec8a62a847a54d7fa7275f@keithp.com>
Reviewed-by: Eric Anholt <96f164ad4d9b2b0dacf8ebee2bb1eeb3aa69adf1@anholt.net>

mapbox/glsl-optimizer,bkaradzic/glsl-optimizer,metora/MesaGLSLCompiler,mcanthony/glsl-optimizer,zeux/glsl-optimizer,dellis1972/glsl-optimizer,bkaradzic/glsl-optimizer,djreep81/glsl-optimizer,zeux/glsl-optimizer,mapbox/glsl-optimizer,jbarczak/glsl-optimizer,zz85/glsl-optimizer,mapbox/glsl-optimizer,djreep81/glsl-optimizer,wolf96/glsl-optimizer,benaadams/glsl-optimizer,djreep81/glsl-optimizer,wolf96/glsl-optimizer,benaadams/glsl-optimizer,zz85/glsl-optimizer,bkaradzic/glsl-optimizer,jbarczak/glsl-optimizer,djreep81/glsl-optimizer,bkaradzic/glsl-optimizer,mapbox/glsl-optimizer,jbarczak/glsl-optimizer,benaadams/glsl-optimizer,wolf96/glsl-optimizer,zz85/glsl-optimizer,benaadams/glsl-optimizer,dellis1972/glsl-optimizer,tokyovigilante/glsl-optimizer,benaadams/glsl-optimizer,dellis1972/glsl-optimizer,zz85/glsl-optimizer,djreep81/glsl-optimizer,metora/MesaGLSLCompiler,tokyovigilante/glsl-optimizer,metora/MesaGLSLCompiler,zeux/glsl-optimizer,benaadams/glsl-optimizer,mcanthony/glsl-optimizer,bkaradzic/glsl-optimizer,dellis1972/glsl-optimizer,zz85/glsl-optimizer,mcanthony/glsl-optimizer,mcanthony/glsl-optimizer,tokyovigilante/glsl-optimizer,tokyovigilante/glsl-optimizer,mapbox/glsl-optimizer,wolf96/glsl-optimizer,zz85/glsl-optimizer,jbarczak/glsl-optimizer,zeux/glsl-optimizer,tokyovigilante/glsl-optimizer,jbarczak/glsl-optimizer,zeux/glsl-optimizer,wolf96/glsl-optimizer,dellis1972/glsl-optimizer,mcanthony/glsl-optimizer