platform/x86: ISST: Fix usage counter

platform/x86: ISST: Fix usage counter

On multi package system, the TPMI SST instance is getting allocated
again as the usage counter is not getting incremented. Here the
instance is allocated only when the usage count is zero. There is
no need to allocate again.

Increment usage ID on successful return from isst_if_cdev_register().

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Link: https://lore.kernel.org/r/20230612224033.2382527-3-srinivas.pandruvada@linux.intel.com
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>