platform/x86: dell-wmi: check for kmalloc() errors

This allocation won't fail in the current kernel because it's small but
not checking for kmalloc() failures introduces static checker warnings
so let's fix it.
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: NMario Limonciello <mario.limonciello@dell.com>
Signed-off-by: NDarren Hart (VMware) <dvhart@infradead.org>

drivers/platform/x86/dell-wmi.c

@@ -639,6 +639,8 @@ static int dell_wmi_events_set_enabled(bool enable)
 	int ret;
 
 	buffer = kzalloc(sizeof(struct calling_interface_buffer), GFP_KERNEL);
+	if (!buffer)
+		return -ENOMEM;
 	buffer->cmd_class = CLASS_INFO;
 	buffer->cmd_select = SELECT_APP_REGISTRATION;
 	buffer->input[0] = 0x10000;