Remove the ARM_DEVICE_MULTIPASS option and make its effect be the default.

Multipass device attachment was tested on many arm platforms by users and
only success was reported on the arm@ mailing list.  This is just the
long-delayed followup of making it the default.

Multipass attachment is necessary when using vendor-supplied FDT data,
because our devices may need to be attached in a different order than they
are described in the FDT data.
Fix CF ERASE breakage caused by 268205.

This prevents BIO_DELETE requests getting stuck in the TRIM queue which
results in a panic on shutdown due to outstanding requests.

PR:		194606
Reported by:	Guido Falsi
Reviewed by:	mav
MFC after:	3 days
Sponsored by:	Multiplay