remove Documentation/smp.txt

After seeing the filename I'd have expected something about the
implementation of SMP in the Linux kernel - not some notes on kernel
configuration and building trivialities noone would search at this
place.

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Acked-by: Alan Cox <alan@redhat.com>
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 6ef54d2..39177ba 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -81,8 +81,8 @@
 	  singleprocessor machines. On a singleprocessor machine, the kernel
 	  will run faster if you say N here.
 
-	  See also the <file:Documentation/smp.txt> and the SMP-HOWTO
-	  available at <http://www.tldp.org/docs.html#howto>.
+	  See also the SMP-HOWTO available at
+	  <http://www.tldp.org/docs.html#howto>.
 
 	  Even if you don't know what to do here, say Y.