iio: frequency: adf4350: cast value to unsigned to make code checkers happy

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

include/linux/iio/frequency/adf4350.h

 /*
  * ADF4350/ADF4351 SPI PLL driver
  *
- * Copyright 2012 Analog Devices Inc.
+ * Copyright 2012-2013 Analog Devices Inc.
  *
  * Licensed under the GPL-2.
  */
@@ -41,7 +41,7 @@
 #define ADF4350_REG2_RDIV2_EN			(1 << 24)
 #define ADF4350_REG2_RMULT2_EN			(1 << 25)
 #define ADF4350_REG2_MUXOUT(x)			((x) << 26)
-#define ADF4350_REG2_NOISE_MODE(x)		((x) << 29)
+#define ADF4350_REG2_NOISE_MODE(x)		(((unsigned)(x)) << 29)
 #define ADF4350_MUXOUT_THREESTATE		0
 #define ADF4350_MUXOUT_DVDD			1
 #define ADF4350_MUXOUT_GND			2