Turns out that IDENTIFY DEVICE and IDENTIFY PACKET DEVICE return data
that's only mostly similar. Specifically word 78 bits are defined for
IDENTIFY DEVICE as
	5 Supports Hardware Feature Control
while a IDENTIFY PACKET DEVICE defines them as
	5 Asynchronous notification supported
Therefore, only pay attention to bit 5 when we're talking to ATAPI
devices (we don't use the hardware feature control at this time).
Ignore it for ATA devices. Remove kludge that papered over this issue
for Samsung SATA SSDs, since Micron drives also have the bit set and
the error was caused by this bad interpretation of the spec (which is
quite easy to do, since bits aren't normally overlapping like this).