libfile: copy_file: Only open regular files with O_TRUNC
Device files can not truncate in the most cases. Check if the
destination is a regular file and open only those with O_TRUNC.
Signed-off-by: Teresa Remmet <t.remmet@phytec.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>