iio: adc: ad4630: Drop some unused register bitfield defines

While working on that driver I noticed that the bitfield described by
AD4630_AVG_FILTER_RESET is actually called "AVG_SYNC" in the reference
manual. Instead of fixing that, remove that unused define and a few more
that are also unused.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>

Author: ukleinek

drivers/iio/adc/ad4630.c

@@ -72,16 +72,11 @@
 #define AD4630_SW_RESET			(BIT(0) | BIT(7))
 /* CHIP GRADE */
 #define AD4630_MSK_CHIP_GRADE		GENMASK(7, 3)
-#define AD4630_CHIP_GRADE(grade)	FIELD_GET(AD4630_MSK_CHIP_GRADE, grade)
 /* MODES */
 #define AD4630_LANE_MODE_MSK		GENMASK(7, 6)
 #define AD4630_CLK_MODE_MSK		GENMASK(5, 4)
 #define AD4630_DATA_RATE_MODE_MSK	BIT(3)
 #define AD4630_OUT_DATA_MODE_MSK	GENMASK(2, 0)
-/* EXIT_CFG_MD */
-#define AD4630_EXIT_CFG_MODE		BIT(0)
-/* AVG */
-#define AD4630_AVG_FILTER_RESET		BIT(7)
 /* OFFSET */
 #define AD4630_REG_CHAN_OFFSET(ch)	(AD4630_REG_OFFSET_X0_2 + 3 * (ch))
 /* HARDWARE_GAIN */