gpu: host1x: mipi: Benefit from devm_clk_get_prepared()

gpu: host1x: mipi: Benefit from devm_clk_get_prepared()

When using devm_clk_get_prepared() instead of devm_clk_get() the clock
is already returned prepared. So probe doesn't need to call
clk_prepare() and at remove time the call to clk_unprepare() can be
dropped. The latter makes the remove callback empty, so it can be
dropped, too.

Acked-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20240409165043.105137-2-u.kleine-koenig@pengutronix.de
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>