[yocto] [meta-xilinx] Update maintainers contact informaton

[Adrian Alonso]

Hi all,

Please welcome Elvis Dowson as new maintainer for meta-xilinx bsp layer.

Elvis had provide fixes over the last months for this layer and I'm pretty
sure that he can improve and move forward this layer.

This BSP layer allows to create a custom Linux distro that can be
deployed in Xilinx FPGA's which can either have a soft-cpu model or a
traditional CPU like PowerPC or ARM Cortex A9.

@Richard, Jeffrey please help Elvis to get write access in this repo.

-- 
Regards
Adrian Alonso
http://aalonso.wordpress.com