clk: mediatek: Register clock gate with device

Allow those clocks under a power domain to do the runtime pm operation
by forwarding the struct device pointer from clock provider.

Signed-off-by: Weiyi Lu <weiyi.lu@mediatek.com>
Link: https://lkml.kernel.org/r/1567414859-3244-2-git-send-email-weiyi.lu@mediatek.com


Signed-off-by: Stephen Boyd <sboyd@kernel.org>