drivers: atm, char fix integer as NULL pointer warnings

drivers/atm/nicstar.c:418:25: warning: Using plain integer as NULL pointer
drivers/char/drm/r128_cce.c:820:25: warning: Using plain integer as NULL pointer
drivers/char/tty_io.c:1183:10: warning: Using plain integer as NULL pointer

Signed-off-by: Harvey Harrison <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/atm/nicstar.c

···
    card->pcidev = pcidev;
    membase = pci_resource_start(pcidev, 1);
    card->membase = ioremap(membase, NS_IOREMAP_SIZE);
-   if (card->membase == 0)
+   if (!card->membase)
    {
       printk("nicstar%d: can't ioremap() membase.\n",i);
       error = 3;

drivers/char/drm/r128_cce.c

···
 	for (i = 0; i < dma->buf_count; i++) {
 		buf = dma->buflist[i];
 		buf_priv = buf->dev_private;
-		if (buf->file_priv == 0)
+		if (!buf->file_priv)
 			return buf;
 	}
 

drivers/char/tty_io.c

···
 		if (*str == ',')
 			str++;
 		if (*str == '\0')
-			str = 0;
+			str = NULL;
 
 		if (tty_line >= 0 && tty_line <= p->num && p->poll_init &&
 				!p->poll_init(p, tty_line, str)) {