devtool: deploy-target: Fix preserving attributes when using --strip

Commit a2db4fa127a3347fc6df31f895fb0b552669119e added ${WORKDIR}/deploy-* to
PSEUDO_IGNORE_PATHS. This breaks the --strip mode since ${D} is copied to
deploy-target-stripped. Use the directory devtool-deploy-target-stripped
instead.

[YOCTO #14451]

Signed-off-by: Florian Amstutz <florian.amstutz@scs.ch>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>