etnaviv: remove dead code

ptiled is always NULL so the if statement is useless.

CoverityID: 1415572
Fixes: b9627765 ("etnaviv: rework compatible render base")
CC: <mesa-stable@lists.freedesktop.org>
Reviewed-by: Jonathan Marek <jonathan@marek.ca>
Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
(cherry picked from commit 1be22083)