clk: rockchip: rk3308: drop unused mux_timer_src_p

clk: rockchip: rk3308: drop unused mux_timer_src_p

The parent names 'mux_timer_src_p' is not used:

  In file included from drivers/clk/rockchip/clk-rk3308.c:13:0:
  drivers/clk/rockchip/clk-rk3308.c:136:7: warning: ‘mux_timer_src_p’ defined but not used [-Wunused-const-variable=]

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20200916161740.14173-6-krzk@kernel.org
Signed-off-by: Heiko Stuebner <heiko@sntech.de>