device-type: allow override bcu_board_name.
We found a few exceptions to hard configure the bcu_board_name, although most of times we can use the default one per devicetype.
E.g. imx8mp, this board is designed as no power monitor support for bcu by default. So, we released to customer another kinds of imx8mp board, which in board level will have power monitor chip. For that kinds of 8mp board, the bcu name would be
imx8mpevkpwra1, not the default
imx8mpevk, this results in different control.
So, this MR allow these rare devices could continue benefit from imx8mp-evk.jinja2 settings, but still could override bcu_board_name in device.jinja2 to fit the bcu tool requirement.