Add MT6779 UART0 clock support.

Fixes: 710774e0 ("clk: mediatek: Add MT6779 clock support")
Signed-off-by: Wendell Lin <wendell.lin@mediatek.com>
Signed-off-by: Hanks Chen <hanks.chen@mediatek.com>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>