cores: mt48lc16m16a2: core is now fetched from micron's url

Import Micron's original file and add patches for:

- update the module declaration (add some parameters),
- add an option for clearing the SDRAM before it is used,
- add tasks to get/set bytes/sorts in the whole memory,
- turn off the debug messages.

Signed-off-by: Franck Jullien <franck.jullien@gmail.com>