ARM: keystone2: Add support for getting external clock dynamically

One some keystone2 platforms like K2G ICE, there is an option
to switch between 24MHz or 25MHz as sysclk. But the existing
driver assumes it is always 24MHz. Add support for getting
all reference clocks dynamically by reading boot pins.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/board/ti/ks2_evm/board_k2hk.c b/board/ti/ks2_evm/board_k2hk.c
index e217bea..b35f24d 100644
--- a/board/ti/ks2_evm/board_k2hk.c
+++ b/board/ti/ks2_evm/board_k2hk.c
@@ -23,6 +23,37 @@
 	[ddr3b_clk]	=	100000000,
 };
 
+unsigned int get_external_clk(u32 clk)
+{
+	unsigned int clk_freq;
+
+	switch (clk) {
+	case sys_clk:
+		clk_freq = 122880000;
+		break;
+	case alt_core_clk:
+		clk_freq = 125000000;
+		break;
+	case pa_clk:
+		clk_freq = 122880000;
+		break;
+	case tetris_clk:
+		clk_freq = 125000000;
+		break;
+	case ddr3a_clk:
+		clk_freq = 100000000;
+		break;
+	case ddr3b_clk:
+		clk_freq = 100000000;
+		break;
+	default:
+		clk_freq = 0;
+		break;
+	}
+
+	return clk_freq;
+}
+
 static struct pll_init_data core_pll_config[NUM_SPDS] = {
 	[SPD800]	= CORE_PLL_799,
 	[SPD1000]	= CORE_PLL_999,