phy: mediatek: mipi-dsi: Use devm variant for of_clk_add_hw_provider()

Switch to devm_of_clk_add_hw_provider() in the probe function: this
also allows to entirely remove the .remove_new() callback, as its
only task was to unregister the clock provider.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20230525115258.90091-3-angelogioacchino.delregno@collabora.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>