mailmap: fix Ricardo's entry

Commit df48b234 (".mailmap: Add all the mail alias for Ricardo
Ribalda") assigned two different proper names for the email address
"ricardo.ribalda@uam.es".  This is a completely wrong usage as the
mailmap feature exists for coalescing together commits by the same
person whose name is sometimes spelled differently.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

.mailmap

@@ -21,7 +21,6 @@ Jagan Teki <jagannadha.sutradharudu-teki@xilinx.com>
 Markus Klotzbuecher <mk@denx.de>
 Prabhakar Kushwaha <prabhakar@freescale.com>
 Rajeshwari Shinde <rajeshwari.s@samsung.com>
-Ricardo Ribalda Delgado <ricardo.ribalda@uam.es>
 Ricardo Ribalda <ricardo.ribalda@uam.es>
 Ricardo Ribalda <ricardo.ribalda@gmail.com>
 Sandeep Paulraj <s-paulraj@ti.com>