MAINTAINERS: Add entry for ULTRATRONIK BOARD SUPPORT

Add a new MAINTAINERS section for the ULTRATRONIK BOARD SUPPORT, covering
the stm32mp157c-ultra-fly-sbc.dts board support file.

This ensures that maintainers of this board are properly listed and can be
notified for any relevant changes.

Signed-off-by: Goran Rađenović <goran.radni@gmail.com>
Signed-off-by: Börge Strümpfel <boerge.struempfel@gmail.com>
Link: https://lore.kernel.org/r/20250508143818.2574558-4-goran.radni@gmail.com
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>

Author: Goran Rađenović

MAINTAINERS

@@ -24752,6 +24752,12 @@ S:	Maintained
 F:	drivers/usb/common/ulpi.c
 F:	include/linux/ulpi/
 
+ULTRATRONIK BOARD SUPPORT
+M:	Goran Rađenović <goran.radni@gmail.com>
+M:	Börge Strümpfel <boerge.struempfel@gmail.com>
+S:	Maintained
+F:	arch/arm/boot/dts/st/stm32mp157c-ultra-fly-sbc.dts
+
 UNICODE SUBSYSTEM
 M:	Gabriel Krisman Bertazi <krisman@kernel.org>
 L:	linux-fsdevel@vger.kernel.org