drivers/misc/ad525x_dpot.c: new features

Add support for AD5270, AD5271, AD5272, AD5274 digital potentiometers.
Add 20-TP feature for AD5291 and AD5292 parts, and update feature list.
AD5291 rdac read back must be shifted by two.

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Chris Verges <chrisv@cyberswitching.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/misc/ad525x_dpot-i2c.c b/drivers/misc/ad525x_dpot-i2c.c
index 374352a..4ff73c2 100644
--- a/drivers/misc/ad525x_dpot-i2c.c
+++ b/drivers/misc/ad525x_dpot-i2c.c
@@ -102,6 +102,8 @@
 	{"ad5170", AD5170_ID},
 	{"ad5172", AD5172_ID},
 	{"ad5173", AD5173_ID},
+	{"ad5272", AD5272_ID},
+	{"ad5274", AD5274_ID},
 	{}
 };
 MODULE_DEVICE_TABLE(i2c, ad_dpot_id);