rtlwifi: remove redundant assignment to variable k

The assignment of 0 to variable k is never read once we break out of
the loop, so the assignment 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>