[MIPS] 0 -> NULL

When comparing a pointer, it's clearer to compare it to NULL than to 0.

Here is an excerpt of the semantic patch:

@@
expression *E;
@@

  E ==
- 0
+ NULL

@@
expression *E;
@@

  E !=
- 0
+ NULL
Signed-off-by: Yoann Padioleau <padator@wanadoo.fr>
Cc: ralf@linux-mips.org
Cc: linux-mips@linux-mips.org
Cc: akpm@linux-foundation.org
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/pci/ops-emma2rh.c

@@ -45,7 +45,7 @@ static int check_args(struct pci_bus *bus, u32 devfn, u32 * bus_num)
 	/* check if the bus is top-level */
 	if (bus->parent != NULL) {
 		*bus_num = bus->number;
-		db_assert(bus_num != 0);
+		db_assert(bus_num != NULL);
 	} else
 		*bus_num = 0;
 

arch/mips/pci/ops-pnx8550.c

@@ -117,7 +117,7 @@ read_config_byte(struct pci_bus *bus, unsigned int devfn, int where, u8 * val)
 	unsigned int data = 0;
 	int err;
 
-	if (bus == 0)
+	if (bus == NULL)
 		return -1;
 
 	err = config_access(PCI_CMD_CONFIG_READ, bus, devfn, where, ~(1 << (where & 3)), &data);
@@ -145,7 +145,7 @@ read_config_word(struct pci_bus *bus, unsigned int devfn, int where, u16 * val)
 	unsigned int data = 0;
 	int err;
 
-	if (bus == 0)
+	if (bus == NULL)
 		return -1;
 
 	if (where & 0x01)
@@ -168,7 +168,7 @@ static int
 read_config_dword(struct pci_bus *bus, unsigned int devfn, int where, u32 * val)
 {
 	int err;
-	if (bus == 0)
+	if (bus == NULL)
 		return -1;
 
 	if (where & 0x03)
@@ -185,7 +185,7 @@ write_config_byte(struct pci_bus *bus, unsigned int devfn, int where, u8 val)
 	unsigned int data = (unsigned int)val;
 	int err;
 
-	if (bus == 0)
+	if (bus == NULL)
 		return -1;
 
 	switch (where & 0x03) {
@@ -213,7 +213,7 @@ write_config_word(struct pci_bus *bus, unsigned int devfn, int where, u16 val)
 	unsigned int data = (unsigned int)val;
 	int err;
 
-	if (bus == 0)
+	if (bus == NULL)
 		return -1;
 
 	if (where & 0x01)
@@ -235,7 +235,7 @@ static int
 write_config_dword(struct pci_bus *bus, unsigned int devfn, int where, u32 val)
 {
 	int err;
-	if (bus == 0)
+	if (bus == NULL)
 		return -1;
 
 	if (where & 0x03)