meta/generate_mipmap: Work-around GLES 1.x problem with GL_DRAW_FRAMEBUFFER
meta/generate_mipmap: Work-around GLES 1.x problem with GL_DRAW_FRAMEBUFFER

GL_DRAW_FRAMEBUFFER does not exist in OpenGL ES 1.x, and since
_mesa_meta_begin hasn't been called yet, we have to work-around API
difficulties.  The whole reason that GL_DRAW_FRAMEBUFFER is used instead
of GL_FRAMEBUFFER is that the read framebuffer may be different.  This
is moot in OpenGL ES 1.x.

I have another patch series that would also fix this (by removing the
calls to _mesa_BindFramebuffer and friends), but it's not quite ready
yet... and I think it may be a bit heavy for some stable branches.
Consider this a stop-gap fix.

Signed-off-by: Ian Romanick <2b237cafb16dc45038e85df6c85e74e6d899eba9@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93215
Cc: "11.0 11.1" <59f39c0db42d4479a46b02d4d2bc11120e37bb44@lists.freedesktop.org>
Reviewed-by: Anuj Phogat <e2026475996c48f0b97fd37e84129b3912980428@gmail.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler