clk: rockchip: rk3036: rename emac ext source clock

There is only support rmii in the RK3036, so we should use the correct
ext clock name as described in the TRM.

Signed-off-by: Xing Zheng <[e-mail]>
[update dt-binding document as well]
Signed-off-by: Heiko Stuebner <[e-mail]>

Documentation/devicetree/bindings/clock/rockchip,rk3036-cru.txt

···
 clock-output-names:
  - "xin24m" - crystal input - required,
  - "ext_i2s" - external I2S clock - optional,
- - "ext_gmac" - external GMAC clock - optional
+ - "rmii_clkin" - external EMAC clock - optional
 
 Example: Clock controller node:
 

drivers/clk/rockchip/clk-rk3036.c

···
 PNAME(mux_uart0_p)	= { "uart0_src", "uart0_frac", "xin24m" };
 PNAME(mux_uart1_p)	= { "uart1_src", "uart1_frac", "xin24m" };
 PNAME(mux_uart2_p)	= { "uart2_src", "uart2_frac", "xin24m" };
-PNAME(mux_mac_p)	= { "mac_pll_src", "ext_gmac" };
+PNAME(mux_mac_p)	= { "mac_pll_src", "rmii_clkin" };
 PNAME(mux_dclk_p)	= { "dclk_lcdc", "dclk_cru" };
 
 static struct rockchip_pll_clock rk3036_pll_clks[] __initdata = {