Obsolete config in kernel build system (XFS_TRACE)

[Christoph Egger]

Hi all!

	As part of the VAMOS[0] research project at the University of
Erlangen we're checking referential integrity between kernel KConfig
options and in-code Conditional blocks.

	Git commit 0b1b213fcf3a8486ada99a2bab84ab8c6f51b264 by
Christoph Hellwig removed all References to CONFIG_XFS_TRACE, which is
unreferenced from KConfig side from the linux source code so there's
only a small bit of it left in KBuild. Mayee remove it as well?

./fs/xfs/Makefile:95
+++>

xfs-$(CONFIG_XFS_TRACE)         += xfs_btree_trace.o

<+++

	Please keep me informed of this patch getting confirmed /
merged so we can keep track of it.

Regards

	Christoph Egger