mx6: tqma6: get board support back to Kconfig build system

mx6: tqma6: get board support back to Kconfig build system

The QS Systems TQMa6 board support was added by commit cb07d74e
and lost by commit e82abaeb.

Commit e82abaeb merged the IMX branch based on pre-Kconfig
and the mainline based on post-Kconfig, simply deleting
the boards.cfg file.  As a result, some boards added just before
the merge were lost.

This commit adds Kconfig, defconfig, MAINTAINERS for TQMa6 board
to work on the Kconfig infrastructure.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Markus Niebel <Markus.Niebel@tq-group.com>
Cc: Stefano Babic <sbabic@denx.de>