Releasing TX/RX descriptor dmamaps during device detachment instead of doing that in bfe_stop().
Releasing TX/RX descriptor dmamaps during device detachment instead of
doing that in bfe_stop().

This should fix a panic recently reported on -current occuring when taking
device down then up.  In the original implementation, an "ifconfig bfe0 down"
triggers bfe_stop(), which also destroys all TX/RX descriptor dmamaps. Hence
the subsequent "ifconfig bfe0 up" would force the device to use those
already-released dmamap and thus panic the kernel.

PR:		kern/77804
Submitted by:	Frank Mayhar <frank at exit dot com>
Reviewed by:	dmlb, sam (mentor)
Tested by:	Phil <pcasidy at casidy dot com>, myself
MFC after:	1 week

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