pds_core: Use struct pdsc for the pdsc_adminq_isr private data

The initial design for the adminq interrupt was done based
on client drivers having their own adminq and adminq
interrupt. So, each client driver's adminq isr would use
their specific adminqcq for the private data struct. For the
time being the design has changed to only use a single
adminq for all clients. So, instead use the struct pdsc for
the private data to simplify things a bit.

This also has the benefit of not dereferencing the adminqcq
to access the pdsc struct when the PDSC_S_STOPPING_DRIVER bit
is set and the adminqcq has actually been cleared/freed.

Fixes: 01ba61b5

 ("pds_core: Add adminq processing and commands")
Signed-off-by: Brett Creeley <brett.creeley@amd.com>
Reviewed-by: Shannon Nelson <shannon.nelson@amd.com>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Link: https://lore.kernel.org/r/20240129234035.69802-4-brett.creeley@amd.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>