[PATCH 04/10] clk: mediatek: mt8183: Add clk mux notifier for MFG mux

[Miles Chen]

> When the MFG PLL clock, which is upstream of the MFG clock, is changed,
> the downstream clock and consumers need to be switched away from the PLL
> over to a stable clock to avoid glitches.
> 
> This is done through the use of the newly added clk mux notifier. The
> notifier is set on the mux itself instead of the upstream PLL, but in
> practice this works, as the rate change notifitcations are propogated
> throughout the sub-tree hanging off the PLL. Just before rate changes,
> the MFG mux is temporarily and transparently switched to the 26 MHz
> main crystal. After the rate change, the mux is switched back.
> 
> Signed-off-by: Chen-Yu Tsai <wenst at chromium.org>
> [Angelo: Rebased to assign clk_ops in mtk_mux_nb]
> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno at collabora.com>
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno at collabora.com>

Reviewed-by: Miles Chen <miles.chen at mediatek.com>