RDMA/usnic: Avoid overly large buffers on stack

It's never a good idea to put a 1000-byte buffer on the kernel stack. The
compiler warns about this instance when usnic_ib_log_vf() gets inlined
into usnic_ib_pci_probe():

drivers/infiniband/hw/usnic/usnic_ib_main.c:543:12: error: stack frame size of 1044 bytes in function 'usnic_ib_pci_probe' [-Werror,-Wframe-larger-than=]

As this is only called for debugging purposes in the setup path, it's
trivial to convert to a dynamic allocation.

Link: https://lore.kernel.org/r/20190906155730.2750200-1-arnd@arndb.de
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/usnic/usnic_ib_main.c

@@ -89,9 +89,15 @@ static void usnic_ib_dump_vf(struct usnic_ib_vf *vf, char *buf, int buf_sz)
 
 void usnic_ib_log_vf(struct usnic_ib_vf *vf)
 {
-	char buf[1000];
-	usnic_ib_dump_vf(vf, buf, sizeof(buf));
+	char *buf = kzalloc(1000, GFP_KERNEL);
+
+	if (!buf)
+		return;
+
+	usnic_ib_dump_vf(vf, buf, 1000);
 	usnic_dbg("%s\n", buf);
+
+	kfree(buf);
 }
 
 /* Start of netdev section */