fdc: Reject unimplemented error actions

drive_init() doesn't permit them for if=floppy, but that's worthless:
we get them via if=none and -global.

This can make device initialization fail.  Since all callers of
fdctrl_init_isa() ignore its value, change it to die instead of
returning failure.  Without this, some callers would ignore the
failure, and others would crash.

Wart: unlike drive_init(), we don't reject the default action when
it's explicitly specified.  That's because we can't distinguish "no
rerror option" from "rerror=report", or "no werror" from
"rerror=enospc".  Left for another day.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
