Change email addresses for B&R Industrial Automation

Change email addresses for B&R Industrial Automation

B&R Industrial Automation has been acquired by ABB in 2017, and this
will be reflected in our email addresses beginning from December 2025.

The email addresses change as follows:
 @br-automation.com -> @<country-code>.abb.com

The existing email addresses will be valid until December 2026.

Add entries for Bernhard Messerklinger and myself to .mailmap, and
update the MAINTAINERS files.

Signed-off-by: Wolfgang Wallner <wolfgang.wallner@br-automation.com>
Signed-off-by: Wolfgang Wallner <wolfgang.wallner@at.abb.com>