drivers/staging/iio: Remove unnecessary semicolon

A simplified version of the semantic patch that finds this problem is as
follows: (http://coccinelle.lip6.fr/

)

// <smpl>
@r1@
statement S;
position p,p1;
@@
S@p1;@p

@script:python r2@
p << r1.p;
p1 << r1.p1;
@@
if p[0].line != p1[0].line_end:
        cocci.include_match(False)
@@
position r1.p;
@@
-;@p
// </smpl>

Signed-off-by: Peter Senna Tschudin <peter.senna@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>