etnaviv: add L8A8_UNORM texture format

No piglit regressions.

CC: <mesa-stable@lists.freedesktop.org>
Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>

src/gallium/drivers/etnaviv/etnaviv_format.c

@@ -103,6 +103,8 @@ static struct etna_format formats[PIPE_FORMAT_COUNT] = {
    _T(B4G4R4A4_UNORM, A4R4G4B4, A4R4G4B4),
    _T(B4G4R4X4_UNORM, X4R4G4B4, X4R4G4B4),
 
+   _T(L8A8_UNORM, A8L8, NONE),
+
    _T(Z16_UNORM,      D16,      A4R4G4B4),
    _T(B5G6R5_UNORM,   R5G6B5,   R5G6B5),
    _T(B5G5R5A1_UNORM, A1R5G5B5, A1R5G5B5),