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svn:author
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gnn
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svn:date
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2015-04-14T14:22:34.532704Z
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When a kernel has DEVICE_POLLING turned on but no drivers have
the capability do not try to take the mutex at all.

Replaces misbegotten attempt from reverted commit 281276

Pointed out by: glebius
Sponsored by: Rubicon Communications (Netgate)
Differential Revision:	https://reviews.freebsd.org/D2262

END