mesa3d: Add temporary fixes for etnaviv rendering

mesa3d: Add temporary fixes for etnaviv rendering

Currently when running Qt5_CinematicExperience demo from Qt5.8 the
covers of the movies appear with a black box instead of showing the
actual art cover.

Also, the fonts are incorrectly displayed in many cases.

Fix these issues by applying temporary patches to etnaviv.

According to Christian Gmeiner and Wladimir J. van der Laan
the correct solution to this problem is to use shader variants [1].

Use these temporary patches until the correct solution appears in
mesa mainline, so that etaniv users can run Qt successfully for
the time being.

[1] https://lists.freedesktop.org/archives/mesa-dev/2017-March/147948.html

Tested on imx6q-sabresd board.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>