RDMA/ucm: Removed checks for unsigned value < 0

cmd is unsigned, no need to check for < 0.  Found by code inspection.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
diff --git a/drivers/infiniband/core/ucma.c b/drivers/infiniband/core/ucma.c
index 71be5ee..b3f3ddd 100644
--- a/drivers/infiniband/core/ucma.c
+++ b/drivers/infiniband/core/ucma.c
@@ -1270,7 +1270,7 @@
 	if (copy_from_user(&hdr, buf, sizeof(hdr)))
 		return -EFAULT;
 
-	if (hdr.cmd < 0 || hdr.cmd >= ARRAY_SIZE(ucma_cmd_table))
+	if (hdr.cmd >= ARRAY_SIZE(ucma_cmd_table))
 		return -EINVAL;
 
 	if (hdr.in + sizeof(hdr) > len)