arm: mx6: tqma6: Extract baseboard configs into separate config file

This patch extracts all baseboard specific defines into a separate config file.
This makes it easier to add other baseboards that use the TQMa6 SoM.

This patch will be used by the upcoming WRU-IV board support which also
uses the TQMa6 SoM.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Markus Niebel <Markus.Niebel@tq-group.com>
Cc: Stefano Babic <sbabic@denx.de>
Acked-By: Markus Niebel <Markus.Niebel@tq-group.com>