tracing/user_events: Use NULL for strstr checks

Trivial fix to ensure strstr checks use NULL instead of 0.

Link: https://lkml.kernel.org/r/[e-mail]

Signed-off-by: Beau Belgrave <[e-mail]>
Signed-off-by: Steven Rostedt (Google) <[e-mail]>

kernel/trace/trace_events_user.c

···
 	goto add_field;
 
 add_validator:
-	if (strstr(type, "char") != 0)
+	if (strstr(type, "char") != NULL)
 		validator_flags |= VALIDATOR_ENSURE_NULL;
 
 	validator = kmalloc(sizeof(*validator), GFP_KERNEL);
···
 		return "%d";
 	if (strcmp(type, "unsigned char") == 0)
 		return "%u";
-	if (strstr(type, "char[") != 0)
+	if (strstr(type, "char[") != NULL)
 		return "%s";
 
 	/* Unknown, likely struct, allowed treat as 64-bit */
···
 
 	return false;
 check:
-	return strstr(type, "char") != 0;
+	return strstr(type, "char") != NULL;
 }
 
 #define LEN_OR_ZERO (len ? len - pos : 0)