[PATCH] docbook build fix

Fix documentation build with `make O='

Cc: Martin Waitz <tali@admingilde.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Documentation/DocBook/Makefile

@@ -49,7 +49,7 @@ installmandocs: mandocs
 KERNELDOC = scripts/kernel-doc
 DOCPROC   = scripts/basic/docproc
 
-XMLTOFLAGS = -m Documentation/DocBook/stylesheet.xsl
+XMLTOFLAGS = -m $(srctree)/Documentation/DocBook/stylesheet.xsl
 #XMLTOFLAGS += --skip-validation
 
 ###