panfrost: Emulated RGTC support
For most GPUs RGTC is disabled, so it needs to be emulated, using the fake_rgtc option of u_transfer_helper.
Passes the rgtc-teximage-01 and rgtc-teximage-02 piglit tests.
With this, only NV_conditional_render
and ARB_texture_buffer_object
will be needed for GL 3.1 to be exposed by default.