phosphor-state-manager: move chassis symlinks to correct subpkg

The `multi-user.target.requires/...Chassis@{i}.service` symlinks were
being added to the `obmc-targets` sub-package, but nothing explicitly
depends on the `chassis` sub-package.  On systems that do not include
the `chassis` sub-package, this results in broken symlinks.

Move these `Chassis@{i}.service` symlinks into the `chassis`
sub-package since that is where the original service file resides.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Iefc8c0bf8eb9b5f43fa67a13bf52ceb4ce55e52e