tile: array underflow in setup_maxnodemem()

My static checker correctly complains that we should have a lower bound
on "node" to prevent an array underflow.

Fixes: 867e359b97 ("arch/tile: core support for Tilera 32-bit chips.")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Chris Metcalf <cmetcalf@mellanox.com>

arch/tile/kernel/setup.c

@@ -140,7 +140,7 @@ static int __init setup_maxnodemem(char *str)
 {
 	char *endp;
 	unsigned long long maxnodemem;
-	long node;
+	unsigned long node;
 
 	node = str ? simple_strtoul(str, &endp, 0) : INT_MAX;
 	if (node >= MAX_NUMNODES || *endp != ':')