glx/dri3: Fix passing renderType into glXCreateContext

Without this, trying to create a GLX_RGBA_FLOAT_TYPE_ARB context would
fail, because GLX_RGBA_TYPE would be a mismatch with the fbconfig.

Cc: mesa-stable@lists.freedesktop.org
Reviewed-by: Tapani Pälli <tapani.palli@intel.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Signed-off-by: Adam Jackson <ajax@redhat.com>
(cherry picked from commit 257edb5b)