staging: dgap: rename and fixup dgap_wait_for_xxx functions

This patch renames and changes the dgap_wait_for_bios and
dgap_wait_for_fep functions from boolean functions to return
zero on success and a negative error code on error.

Signed-off-by: Mark Hounschell <markh@compro.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>