PCI: acpiphp: Allow built-in drivers for Attention Indicators

Since the introduction of the attention callback in acpiphp, a non-zero
struct module *owner has been required in acpiphp_register_attention(). The
intent seemed to be that the core code could hold a refcount on the module
while invoking a callback.

This check accidentally precludes the possibility of attention callbacks to
built-in drivers.

Remove the check on `struct module *owner` in acpiphp_register_attention()
so attention callbacks can also be registered from built-in drivers.

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: D Scott Phillips <[e-mail]>
Signed-off-by: Bjorn Helgaas <[e-mail]>

drivers/pci/hotplug/acpiphp_core.c

···
 {
 	int retval = -EINVAL;
 
-	if (info && info->owner && info->set_attn &&
-			info->get_attn && !attention_info) {
+	if (info && info->set_attn && info->get_attn && !attention_info) {
 		retval = 0;
 		attention_info = info;
 	}