staging:iio:meter:ade7753 should be 16 bit read not 8 bit for mode register.

Build tested only.

Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Reported-by: Randy Dunlap <rdunlap@xenotime.net>
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Acked-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>