staging: rtl8192u: ieee80211: Fix spelling mistake

Replace explicitely with explicitly to get rid of checkpatch warning.

Signed-off-by: Vatsala Narang <vatsalanarang@gmail.com>
Acked-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>