ACPI: Fix sparse warnings

Use NULL for pointers

drivers/acpi/osl.c:208:10: warning: Using plain integer as NULL pointer
drivers/acpi/tables/tbxface.c:411:49: warning: Using plain integer as NULL pointer
drivers/acpi/processor_core.c:1008:10: warning: Using plain integer as NULL pointer

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/osl.c

@@ -205,7 +205,7 @@ void __iomem *acpi_os_map_memory(acpi_physical_address phys, acpi_size size)
 {
 	if (phys > ULONG_MAX) {
 		printk(KERN_ERR PREFIX "Cannot map memory that high\n");
-		return 0;
+		return NULL;
 	}
 	if (acpi_gbl_permanent_mmap)
 		/*

drivers/acpi/processor_core.c

@@ -1005,7 +1005,7 @@ static int __init acpi_processor_init(void)
 #ifdef CONFIG_SMP
 	if (ACPI_FAILURE(acpi_get_table(ACPI_SIG_MADT, 0,
 				(struct acpi_table_header **)&madt)))
-		madt = 0;
+		madt = NULL;
 #endif
 
 	acpi_processor_dir = proc_mkdir(ACPI_PROCESSOR_CLASS, acpi_root_dir);

drivers/acpi/tables/tbxface.c

@@ -408,7 +408,7 @@ acpi_get_table(char *signature,
 		}
 
 		if (!acpi_gbl_permanent_mmap) {
-			acpi_gbl_root_table_list.tables[i].pointer = 0;
+			acpi_gbl_root_table_list.tables[i].pointer = NULL;
 		}
 
 		return (status);