Staging: iio: ade7758: Remove braces on a single statement if

This patch fixes the checkpatch.pl warning:

WARNING: braces {} are not necessary for single
statement blocks

Signed-off-by: Taiane Coelho Ramos <exhora.tat@gmail.com>
Reviewed-by: Daniel Baluta <daniel.baluta@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>