staging: ks7010: Factor out repeated code for reading IEs.

Some of the code for reading IEs is replicated multiple times in the
switch statement for get_ap_information().  Factor that code out into
read_ie().

Signed-off-by: Quytelda Kahja <quytelda@tamalin.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>