tools: binman: ti_board_cfg: improve error message

When there is a lint error the user gets the following cryptic message:

  binman: Node '/path/to/some/node': Yamllint error: 18: comments

This isn't very helpful. Improve the message to tell the user that the
number is actually a line number and also tell the user in which file
they have to look.

Signed-off-by: Michael Walle <mwalle@kernel.org>
Reviewed-by: Neha Malcom Francis <n-francis@ti.com>