[MIPS] Alchemy: Fix ids in Alchemy db dma device table

0 is a valid device id (DSCR_CMD0_UART0_TX), so we can't use it to mark
an empty entry in the device table. Use ~0 instead and search for id ~0
when looking for a free entry.
Signed-off-by: Wolfgang Ocker <weo@reccoware.de>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/au1000/common/dbdma.c

@@ -161,22 +161,22 @@ static dbdev_tab_t dbdev_tab[] = {
 	{ DSCR_CMD0_ALWAYS, DEV_FLAGS_ANYUSE, 0, 0, 0x00000000, 0, 0 },
 
 	/* Provide 16 user definable device types */
-	{ 0, 0, 0, 0, 0, 0, 0 },
-	{ 0, 0, 0, 0, 0, 0, 0 },
-	{ 0, 0, 0, 0, 0, 0, 0 },
-	{ 0, 0, 0, 0, 0, 0, 0 },
-	{ 0, 0, 0, 0, 0, 0, 0 },
-	{ 0, 0, 0, 0, 0, 0, 0 },
-	{ 0, 0, 0, 0, 0, 0, 0 },
-	{ 0, 0, 0, 0, 0, 0, 0 },
-	{ 0, 0, 0, 0, 0, 0, 0 },
-	{ 0, 0, 0, 0, 0, 0, 0 },
-	{ 0, 0, 0, 0, 0, 0, 0 },
-	{ 0, 0, 0, 0, 0, 0, 0 },
-	{ 0, 0, 0, 0, 0, 0, 0 },
-	{ 0, 0, 0, 0, 0, 0, 0 },
-	{ 0, 0, 0, 0, 0, 0, 0 },
-	{ 0, 0, 0, 0, 0, 0, 0 },
+	{ ~0, 0, 0, 0, 0, 0, 0 },
+	{ ~0, 0, 0, 0, 0, 0, 0 },
+	{ ~0, 0, 0, 0, 0, 0, 0 },
+	{ ~0, 0, 0, 0, 0, 0, 0 },
+	{ ~0, 0, 0, 0, 0, 0, 0 },
+	{ ~0, 0, 0, 0, 0, 0, 0 },
+	{ ~0, 0, 0, 0, 0, 0, 0 },
+	{ ~0, 0, 0, 0, 0, 0, 0 },
+	{ ~0, 0, 0, 0, 0, 0, 0 },
+	{ ~0, 0, 0, 0, 0, 0, 0 },
+	{ ~0, 0, 0, 0, 0, 0, 0 },
+	{ ~0, 0, 0, 0, 0, 0, 0 },
+	{ ~0, 0, 0, 0, 0, 0, 0 },
+	{ ~0, 0, 0, 0, 0, 0, 0 },
+	{ ~0, 0, 0, 0, 0, 0, 0 },
+	{ ~0, 0, 0, 0, 0, 0, 0 },
 };
 
 #define DBDEV_TAB_SIZE	ARRAY_SIZE(dbdev_tab)
@@ -209,7 +209,7 @@ au1xxx_ddma_add_device(dbdev_tab_t *dev)
 	dbdev_tab_t *p=NULL;
 	static u16 new_id=0x1000;
 
-	p = find_dbdev_id(0);
+	p = find_dbdev_id(~0);
 	if ( NULL != p )
 	{
 		memcpy(p, dev, sizeof(dbdev_tab_t));