iio: dac: ti-dac5571 remove redundant variable 'shift'

Variable shift is being assigned but is never used hence it is
redundant and can be removed.

Cleans up two clang warnings:
warning: variable ‘shift’ set but not used [-Wunused-but-set-variable]
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Reviewed-by: NSean Nyekjaer <sean.nyekjaer@prevas.dk>
Signed-off-by: NJonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/dac/ti-dac5571.c

@@ -97,9 +97,6 @@ static int dac5571_cmd_quad(struct dac5571_data *data, int channel, u16 val)
 
 static int dac5571_pwrdwn_single(struct dac5571_data *data, int channel, u8 pwrdwn)
 {
-	unsigned int shift;
-
-	shift = 12 - data->spec->resolution;
 	data->buf[1] = 0;
 	data->buf[0] = pwrdwn << DAC5571_SINGLE_PWRDWN_BITS;
 
@@ -111,9 +108,6 @@ static int dac5571_pwrdwn_single(struct dac5571_data *data, int channel, u8 pwrd
 
 static int dac5571_pwrdwn_quad(struct dac5571_data *data, int channel, u8 pwrdwn)
 {
-	unsigned int shift;
-
-	shift = 16 - data->spec->resolution;
 	data->buf[2] = 0;
 	data->buf[1] = pwrdwn << DAC5571_QUAD_PWRDWN_BITS;
 	data->buf[0] = (channel << DAC5571_CHANNEL_SELECT) |