Fix off-by-one error (introduced in r1.60) that had the effect of disallowing a read of exactly MAXPHYS bytes.
Fix off-by-one error (introduced in r1.60) that had the effect of
disallowing a read of exactly MAXPHYS bytes.

Reviewed by:	des, rdivacky
MFC after:	1 week
Sponsored by:	nCircle Network Security

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