powerpc: Modify MPC52xx maintainers entry to cover all MPC5xxx parts

Linux now supports the MPC5121 part and is handled by the same
maintainer.  Update MAINTAINERS to reflect this.  Also remove URLs
which are out of date or are not particularly relevant.
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>

MAINTAINERS

@@ -2489,13 +2489,11 @@ W:	http://www.penguinppc.org/
 L:	linuxppc-dev@ozlabs.org
 S:	Maintained
 
-LINUX FOR POWERPC EMBEDDED MPC52XX
+LINUX FOR POWERPC EMBEDDED MPC5XXX
 P:	Sylvain Munaut
 M:	tnt@246tNt.com
 P:	Grant Likely
 M:	grant.likely@secretlab.ca
-W:	http://www.246tNt.com/mpc52xx/
-W:	http://www.penguinppc.org/
 L:	linuxppc-dev@ozlabs.org
 S:	Maintained