staging:rtl8192u: Remove potential memory leak

Add call to ieee80211_networks_free() to avoid potential memory
leak if allocation of pHTInfo fails.

If the third allocation fails only the first successful allocation
is freed, not the second.

Signed-off-by: John Whitmore <johnfwhitmore@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>