Handle Programmable Early Warning for control commands in sa(4).

When the tape position is inside the Early Warning area, the tape
drive will return a sense key of NO SENSE, and an ASC/ASCQ of
0x00,0x02, which means: End-of-partition/medium detected". If
this was in response to a control command like WRITE FILEMARKS,
we correctly translate this as informational status and return
0 from saerror().

Programmable Early Warning should be handled the same way, but
we weren't handling it that way. As a result, if a PEW status
(sense key of NO SENSE, ASC/ASCQ of 0x00,0x07, "Programmable early
warning detected") came back in response to a WRITE FILEMARKS,
we returned an error.

The impact of this was that if an application was writing to a
sa(4) device, and a PEW area was set (in the Device Configuration
Extension subpage -- mode page 0x10, subpage 1), and a filemark
needed to be written on close, we could wind up returning an error
to the user on close because of a "failure" to write the filemarks.

It actually isn't a failure, but rather just a status report from
the drive, and shouldn't be treated as a failure.

sys/cam/scsi/scsi_sa.c:
For control commands in saerror(), treat asc/ascq 0x00,0x07
the same as 0x00,{0-5} -- not an error. Return 0, since
the command actually did succeed.

Reported by: Dr. Andreas Haakh <andreas@haakh.de>
Tested by: Dr. Andreas Haakh <andreas@haakh.de>
Sponsored by: Spectra Logic
MFC after: 3 days