intel/blorp_blit: Fix max blit size for gen6
intel/blorp_blit: Fix max blit size for gen6

Fixes ES3-CTS.gtf.GL3Tests.framebuffer_blit.framebuffer_blit_functionality_stencil_blit

Signed-off-by: Jordan Justen <a79006884ba9cf5f4f7fcbb92a15b208780d8c97@intel.com>
Reviewed-by: Lionel Landwerlin <9463032a5b99ffad10f36631678a833369a311b5@intel.com>
Reviewed-by: Kenneth Graunke <bd2562f754ec92342f93f61c25d731e290a2ffa8@whitecape.org>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler