iwlwifi: make various functions void in the file rs.c

This makes various functions in the file rs.c void due to these
functions never returning a error code to signal to their callers
if and how they have failed to complete their intended work.

Signed-off-by: Nicholas Krause <xerofoify@gmail.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>