clk: sunxi-ng: h616: Reparent GPU clock during frequency changes

In the Linux kernel, the following vulnerability has been resolved:

clk: sunxi-ng: h616: Reparent GPU clock during frequency changes

The H616 manual does not state that the GPU PLL supports dynamic frequency configuration, so we must take extra care when changing the frequency. Currently any attempt to do device DVFS on the GPU lead to panfrost various ooops, and GPU hangs.

The manual describes the algorithm for changing the PLL frequency, which the CPU PLL notifier code already support, so we reuse that to reparent the GPU clock to GPU1 clock during frequency changes.