ipw2x00: remove redundant assignment to err

Variable err is initialized to a value that is never read and it
is re-assigned later.  The initialization is redundant and can
be removed.

Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>