ptp: vmw: Drop ptp_vmw_acpi_device

Static variable ptp_vmw_acpi_device in the ptp_vmw driver is assigned,
but never used, so drop it.

No functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://patch.msgid.link/24384916.6Emhk5qWAg@rafael.j.wysocki
Signed-off-by: Jakub Kicinski <kuba@kernel.org>