iio: adc: replace comma with a semicolon

Replace a comma between expression statements by a semicolon. This
changes the semantics of the code, but given the current indentation
appears to be what is intended.
A simplified version of the Coccinelle semantic patch that performs this
transformation is as follows:

// <smpl>
@r@
expression e1,e2;
@@

 e1
-,
+;
 e2;
// </smpl>

Signed-off-by: Arushi Singhal <arushisinghal19971997@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>