Documentation: nfsroot.rst: Fix references to nfsroot.rst

When converting and moving nfsroot.txt to nfsroot.rst the references to
the old text file was not updated to match the change, fix this.

Fixes: f9a9349846f92b2d ("Documentation: nfsroot.txt: convert to ReST")
Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20200212181332.520545-1-niklas.soderlund+renesas@ragnatech.se
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig
index f96bd48..fb1dc8d 100644
--- a/net/ipv4/Kconfig
+++ b/net/ipv4/Kconfig
@@ -129,7 +129,7 @@
 
 	  If unsure, say Y. Note that if you want to use DHCP, a DHCP server
 	  must be operating on your network.  Read
-	  <file:Documentation/filesystems/nfs/nfsroot.txt> for details.
+	  <file:Documentation/admin-guide/nfs/nfsroot.rst> for details.
 
 config IP_PNP_BOOTP
 	bool "IP: BOOTP support"
@@ -144,7 +144,7 @@
 	  does BOOTP itself, providing all necessary information on the kernel
 	  command line, you can say N here. If unsure, say Y. Note that if you
 	  want to use BOOTP, a BOOTP server must be operating on your network.
-	  Read <file:Documentation/filesystems/nfs/nfsroot.txt> for details.
+	  Read <file:Documentation/admin-guide/nfs/nfsroot.rst> for details.
 
 config IP_PNP_RARP
 	bool "IP: RARP support"
@@ -157,7 +157,7 @@
 	  older protocol which is being obsoleted by BOOTP and DHCP), say Y
 	  here. Note that if you want to use RARP, a RARP server must be
 	  operating on your network. Read
-	  <file:Documentation/filesystems/nfs/nfsroot.txt> for details.
+	  <file:Documentation/admin-guide/nfs/nfsroot.rst> for details.
 
 config NET_IPIP
 	tristate "IP: tunneling"