MFC: 279097
MFC: 279097

sfxge: check allocations are non-NULL before freeing them

Caught when efx_filter_init() failed and called efx_filter_fini() in the
teardown path.

Submitted by:   Andrew Lee <alee at solarflare.com>
Sponsored by:   Solarflare Communications, Inc.
Approved by:    gnn (mentor)

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