parisc: Fix crash when calling PDC_PAT_MEM PDT firmware function

parisc: Fix crash when calling PDC_PAT_MEM PDT firmware function

Commit 31b8819bbcee ("parisc: Add Page Deallocation Table (PDT) support")
introduced the pdc_pat_mem_read_pd_pdt() firmware helper function, which
crashed the system because it trashed the stack if the
pdc_pat_mem_read_pd_retinfo struct was located on the stack (and which is
in size less than the required 32 64-bit values).

Fix it by using the pdc_result struct instead when calling firmware and copy
the return values back into the result struct when finished sucessfully.

While debugging this code I noticed that the pdc_type wasn't set correctly
either, so let's fix that too.

Fixes: 31b8819bbcee ("parisc: Add Page Deallocation Table (PDT) support")
Signed-off-by: Helge Deller <deller@gmx.de>