packaged-staging: Fix packagaging of cross packages

packaged-staging: Fix packagaging of cross packages

packagedstaging_fastpath() was only copying the contents of CROSS_DIR to
PSTAGE_TMPDIR resulting in the folders contents being packaged and then
installed incorrectly at the top level of CROSS_DIR rather than in HOST_ARCH
specific sub directories.

This patch fixes that issue by copying the directory and its contents rather
than just the directory contents.

Signed-off-by: Joshua Lock <josh@linux.intel.com>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>