toshiba_acpi: make remove_device() and add_device() void

remove_device() and add_device() are not related to ACPI APIs, it does not
make sense to return acpi_status for both functions.

Current implementation of add_device() always AE_OK, thus the return value
checking for add_device() always return false for ACPI_FAILURE(status).
This patch makes add_device() to be void and remove the unnecessary return
value checking.

remove_proc_entry() won't fail, thus change remove_device() to be void.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Cc: Matthew Garrett <mjg@redhat.com>
Cc: Márton Németh <nm127@freemail.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Matthew Garrett <mjg@redhat.com>