Fix single linked list manipulation for sub_driver.  If the remving entry
is not on the head of the sub_driver list, it goes into infinate loop.

Though that infinite loop doesn't happen.  Because the only user of
acpi_pci_register_dirver() is acpiphp.
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Len Brown <len.brown@intel.com>