cpu/allwinner/a10: Add helper to configure CPU clock

Change-Id: I5a3bb3220aeefdd6822a7dbecf210ff77095dad6
Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-on: http://review.coreboot.org/4685
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/cpu/allwinner/a10/clock.h

@@ -256,4 +256,7 @@ void a1x_pll5_enable_dram_clock_output(void);
 void a1x_ungate_dram_clock_output(void);
 void a1x_gate_dram_clock_output(void);
 
+/* Not available in bootblock */
+void a1x_set_cpu_clock(u16 cpu_clk_mhz);
+
 #endif				/* CPU_ALLWINNER_A10_CLOCK_H */