staging: wilc1000: fix unchecked return value

staging: wilc1000: fix unchecked return value

[ Upstream commit 9e96652756ad647b7bcc03cb99ffc9756d7b5f93 ]

Function dev_alloc_skb() will return a NULL pointer if there is no
enough memory. However, in function WILC_WFI_mon_xmit(), its return
value is used without validation. This may result in a bad memory access
bug. This patch fixes the bug.

Signed-off-by: Pan Bian <bianpan2016@163.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>