Staging: media: Use !x in place of NULL comparision

Test for NULL as !x instead of NULL comparisions for
functions that return NULL on failure.
Issue found using coccinelle
Semantic patch used to solve the problem is as follows

// <smpl>
@@
expression x;
statement S;
@@

x = (\(kmalloc\|devm_kzalloc\|kmalloc_array\|devm_ioremap\|
usb_alloc_urb\|alloc_netdev\|dev_alloc_skb\)(...));

-if(x==NULL)
+if(!x)
// </smpl>

Signed-off-by: Bhanusree Pola <bhanusreemahesh@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>