drm/etnaviv: fix tx clock gating on some GC7000 variants

drm/etnaviv: fix tx clock gating on some GC7000 variants

[ Upstream commit d7a5c9de99b3a9a43dce49f2084eb69b5f6a9752 ]

commit 4bce244272513 ("drm/etnaviv: disable tx clock gating for GC7000
rev6203") accidentally applied the fix for i.MX8MN errata ERR050226 to
GC2000 instead of GC7000, failing to disable tx clock gating for GC7000
rev 0x6023 as intended.

Additional clean-up further propagated this issue, partially breaking
the clock gating fixes added for GC7000 rev 6202 in commit 432f51e7deeda
("drm/etnaviv: add clock gating workaround for GC7000 r6202").

Signed-off-by: Derek Foreman <derek.foreman@collabora.com>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>