devtool: deploy-target: don't specify ssh/scp port unless user does

devtool: deploy-target: don't specify ssh/scp port unless user does

If the user doesn't specify a port then we should avoid specifying one
on the ssh/scp command line in case the user has configured one for the
host they are connecting to, which was being overridden unnecessarily.

Fixes [YOCTO #12381].

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>