rename MAME 2014 assets to MAME 2015 name
Created by: markwkidd
This PR follows the merge of https://github.com/libretro/libretro-super/pull/940 which initiated the process.
The PRs relevant to the name update are:
- MAME 2014 repo: https://github.com/libretro/mame2014-libretro/pull/73
- libretro-super repo: https://github.com/libretro/libretro-super/pull/942
- libretro-database repo:
https://github.com/libretro/libretro-database/pull/787Merged - retroarch-assets repo: https://github.com/libretro/retroarch-assets/pull/289