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/arch/arm/mach-keystone/include/mach/clock.h b/arch/arm/mach-keystone/include/mach/clock.h
index 0d8a944..006d074 100644
--- a/arch/arm/mach-keystone/include/mach/clock.h
+++ b/arch/arm/mach-keystone/include/mach/clock.h
@@ -117,7 +117,6 @@
 	int pll_od;		/* PLL output divider */
 };
 
-extern unsigned int external_clk[ext_clk_count];
 extern const struct keystone_pll_regs keystone_pll_regs[];
 extern s16 divn_val[];
 extern int speeds[];
@@ -129,6 +128,7 @@
 int get_max_dev_speed(int *spds);
 int get_max_arm_speed(int *spds);
 void pll_pa_clk_sel(void);
+unsigned int get_external_clk(u32 clk);
 
 #endif
 #endif