devtool: Fix _copy_file() TypeError

when devtool finish, the _copy_file() failed.
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TypeError: _copy_file() got an unexpected keyword argument
'base_outdir'
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Fixes: 05f2d5d2 ("devtool: finish: add dry-run option")

Signed-off-by: Xiaobing Luo <luoxiaobing0926@gmail.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit a45d9dc0)
Signed-off-by: Steve Sakoman <steve@sakoman.com>