mesa: support GL_RED/GL_RG in ES2 contexts when driver support exists

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93126
Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Eduardo Lima Mitev <elima@igalia.com>
Cc: "11.0 11.1" <mesa-stable@lists.freedesktop.org>
4 files changed