acpi_ec(4): Don't probe erroneously if success occurred

In r360131, acpi_ec probe was changed to not clobber an error status prior to
several error cases that did not explicitly set the error variable before
goto'ing the exit path.  However, I did not notice that the error variable was
not set to success in the success path.  That caused all successful probes to
fail, which is obviously undesirable.

PR:		245778
Reported by:	Neel Chauhan <neel AT neelc.org>, Evilham <contact AT evilham.com>
Tested by:	Evilham
X-MFC-With:	r360131

sys/dev/acpica/acpi_ec.c

@@ -443,6 +443,8 @@ acpi_ec_probe(device_t dev)
 
     if (buf.Pointer)
 	AcpiOsFree(buf.Pointer);
+
+    ret = rc;
 out:
     if (ret <= 0) {
 	snprintf(desc, sizeof(desc), "Embedded Controller: GPE %#x%s%s",