update readme wrt ext2/ext4 usage

SVN-Revision: 25482

target/linux/uml/README

@@ -11,13 +11,13 @@ This is a first stab at a build that 'just works' and there will be more
 cleanup to come.  The simple directions are:-
 
 Configure for uml target
-Configure with an ext2 root file system
+Configure with an ext4 root file system
 build it all
 
-In your bin directory you will find a kernel and an ext2 root file system
+In your bin directory you will find a kernel and an ext4 root file system
 when it's finished.  Just run it like this:-
 
-bin/uml/openwrt-uml-vmlinux ubd0=bin/uml/openwrt-uml-ext2.img con=null ssl=null ssl0=fd:0,fd:1 con0=null,fd:2
+bin/uml/openwrt-uml-vmlinux ubd0=bin/uml/openwrt-uml-ext4.img con=null ssl=null ssl0=fd:0,fd:1 con0=null,fd:2
 
 The uml will start, and eventually the serial console of the uml will be at your
 console prompt.  If you would like it in xterms, substitute con=xterm and con0=xterm.