ARM: imx6q: add the missing cko output selection

The clock output on imx6q CCM_CLKO1 pad is not always cko1 clock, and
there is a multiplexer to select between cko1 and cko2.  Add this
missing selection as the clock cko.
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

Documentation/devicetree/bindings/clock/imx6q-clock.txt

@@ -213,6 +213,7 @@ clocks and IDs.
 	cko2_sel      		198
 	cko2_podf      		199
 	cko2      		200
+	cko      		201
 
 Examples:
 

arch/arm/mach-imx/clk-imx6q.c

@@ -216,6 +216,7 @@ static const char *cko2_sels[] = {
 	"ldb_di0", "ldb_di1", "esai", "eim_slow",
 	"uart_serial", "spdif", "asrc", "hsi_tx",
 };
+static const char *cko_sels[] = { "cko1", "cko2", };
 
 enum mx6q_clks {
 	dummy, ckil, ckih, osc, pll2_pfd0_352m, pll2_pfd1_594m, pll2_pfd2_396m,
@@ -250,7 +251,7 @@ enum mx6q_clks {
 	ssi2_ipg, ssi3_ipg, rom, usbphy1, usbphy2, ldb_di0_div_3_5, ldb_di1_div_3_5,
 	sata_ref, sata_ref_100m, pcie_ref, pcie_ref_125m, enet_ref, usbphy1_gate,
 	usbphy2_gate, pll4_post_div, pll5_post_div, pll5_video_div, eim_slow,
-	spdif, cko2_sel, cko2_podf, cko2, clk_max
+	spdif, cko2_sel, cko2_podf, cko2, cko, clk_max
 };
 
 static struct clk *clk[clk_max];
@@ -409,6 +410,7 @@ static void __init imx6q_clocks_init(struct device_node *ccm_node)
 	clk[vpu_axi_sel]      = imx_clk_mux("vpu_axi_sel",      base + 0x18, 14, 2, vpu_axi_sels,      ARRAY_SIZE(vpu_axi_sels));
 	clk[cko1_sel]         = imx_clk_mux("cko1_sel",         base + 0x60, 0,  4, cko1_sels,         ARRAY_SIZE(cko1_sels));
 	clk[cko2_sel]         = imx_clk_mux("cko2_sel",         base + 0x60, 16, 5, cko2_sels,         ARRAY_SIZE(cko2_sels));
+	clk[cko]              = imx_clk_mux("cko",              base + 0x60, 8, 1,  cko_sels,          ARRAY_SIZE(cko_sels));
 
 	/*                              name         reg      shift width busy: reg, shift parent_names  num_parents */
 	clk[periph]  = imx_clk_busy_mux("periph",  base + 0x14, 25,  1,   base + 0x48, 5,  periph_sels,  ARRAY_SIZE(periph_sels));