.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: NRicardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus 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>