xilinx: Consolidate board_fit_config_name_match() for Xilinx platforms

Move board_fit_config_name_match() from Zynq/ZynqMP to common location.
This change will open a way to use it also by Microblaze and Versal.
Through this function there is a way to handle images with multiple DTBs.
For now match it with DEVICE_TREE as is done for Zynq.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>