Driver ad6676.c warnings

There are 2 warnings in the ad6676.c driver compiling time:

drivers/iio/adc/ad6676.c: In function 'ad6676_shuffle_setup':

drivers/iio/adc/ad6676.c:408:11: warning: 'reg_val' may be used uninitialized in this function [-Wuninitialized]

drivers/iio/adc/ad6676.c: In function 'ad6676_extinfo_write':

drivers/iio/adc/ad6676.c:710:5: warning: 'update' may be used uninitialized in this function [-Wuninitialized]

I've initialized both variables by 0;