efi_loader: allow return value in EFI_CALL

Macro EFI_CALL was introduced to call an UEFI function.
Unfortunately it does not support return values.
Most UEFI functions have a return value.

So let's rename EFI_CALL to EFI_CALL_VOID and introduce a
new EFI_CALL macro that supports return values.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Alexander Graf <agraf@suse.de>
diff --git a/lib/efi_loader/efi_boottime.c b/lib/efi_loader/efi_boottime.c
index 90e9ead..2c9379a 100644
--- a/lib/efi_loader/efi_boottime.c
+++ b/lib/efi_loader/efi_boottime.c
@@ -163,7 +163,8 @@
 		return;
 	event->signaled = 1;
 	if (event->type & EVT_NOTIFY_SIGNAL) {
-		EFI_CALL(event->notify_function(event, event->notify_context));
+		EFI_CALL_VOID(event->notify_function(event,
+						     event->notify_context));
 	}
 }