MAINTAINERS: Add myself as maintainer of the Ralink architecture

Its been a while since I am making contributions to this architecture.
Hence add myself as maintainer.

Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Acked-by: John Crispin <john@phrozen.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

Author: paraka

MAINTAINERS

@@ -18051,6 +18051,7 @@ F:	drivers/media/cec/usb/rainshadow/
 
 RALINK MIPS ARCHITECTURE
 M:	John Crispin <john@phrozen.org>
+M:	Sergio Paracuellos <sergio.paracuellos@gmail.com>
 L:	linux-mips@vger.kernel.org
 S:	Maintained
 F:	arch/mips/ralink