clk_k210.c: Clean up how we handle nop

Now that sandbox has <asm/barrier.h> and defines nop() there we should
include that in our driver for clarity and then remove our local nop()
from <k210/pll.h>.

Reviewed-by: Sean Anderson <[e-mail]>
Signed-off-by: Tom Rini <[e-mail]>

drivers/clk/clk_k210.c

···
 #include <dt-bindings/mfd/k210-sysctl.h>
 #include <k210/pll.h>
 #include <linux/bitfield.h>
+#include <asm/barrier.h>
 
 DECLARE_GLOBAL_DATA_PTR;
 

include/k210/pll.h

···
 #ifdef CONFIG_UNIT_TEST
 TEST_STATIC int k210_pll_calc_config(u32 rate, u32 rate_in,
 				     struct k210_pll_config *best);
-#ifndef nop
-#define nop()
-#endif
 
 #endif
 #endif /* K210_PLL_H */