net: fix NetConsole documentation reference

Fixes: d0253f7 ("doc: move README.NetConsole to HTML documentation")
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>

net/Kconfig

@@ -57,7 +57,7 @@ config NETCONSOLE
 	bool "NetConsole support"
 	help
 	  Support the 'nc' input/output device for networked console.
-	  See README.NetConsole for details.
+	  See doc/usage/netconsole.rst for details.
 
 config IP_DEFRAG
 	bool "Support IP datagram reassembly"