.mailmap: add Ricardo Ribalda

Work and Home computer had different settings in the mail client.  Some
contributions appear as Ricardo Ribalda, others as Ricardo Ribalda Delgado
(and one as just Ricardo).
Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

.mailmap

@@ -100,6 +100,7 @@ Rajesh Shah <rajesh.shah@intel.com>
 Ralf Baechle <ralf@linux-mips.org>
 Ralf Wildenhues <Ralf.Wildenhues@gmx.de>
 Rémi Denis-Courmont <rdenis@simphalempin.com>
+Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
 Rudolf Marek <R.Marek@sh.cvut.cz>
 Rui Saraiva <rmps@joel.ist.utl.pt>
 Sachin P Sant <ssant@in.ibm.com>