ARM: OMAP: Fix compiler error when I2C_OMAP is not set

Fix compiler error when I2C_OMAP is not set
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Jarkko Nikula <jarkko.nikula@nokia.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

include/asm-arm/arch-omap/common.h

@@ -36,8 +36,12 @@ struct sys_timer;
 extern void omap_map_common_io(void);
 extern struct sys_timer omap_timer;
 extern void omap_serial_init(void);
+#ifdef CONFIG_I2C_OMAP
 extern int omap_register_i2c_bus(int bus_id, u32 clkrate,
 				 struct i2c_board_info const *info,
 				 unsigned len);
+#else
+#define omap_register_i2c_bus(...)	do { } while (0)
+#endif
 
 #endif /* __ARCH_ARM_MACH_OMAP_COMMON_H */