cxl/pci: Handle truncated CDAT header

cxl_cdat_get_length() only checks whether the DOE response size is
sufficient for the Table Access response header (1 dword), but not the
succeeding CDAT header (1 dword length plus other fields).

It thus returns whatever uninitialized memory happens to be on the stack
if a truncated DOE response with only 1 dword was received. Fix it.

Fixes: c97006046c79 ("cxl/port: Read CDAT table")
Reported-by: Ming Li <[e-mail]>
Tested-by: Ira Weiny <[e-mail]>
Signed-off-by: Lukas Wunner <[e-mail]>
Reviewed-by: Ming Li <[e-mail]>
Reviewed-by: Dan Williams <[e-mail]>
Reviewed-by: Jonathan Cameron <[e-mail]>
Cc: [e-mail] # v6.0+
Reviewed-by: Kuppuswamy Sathyanarayanan <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Dan Williams <[e-mail]>

drivers/cxl/core/pci.c

···
 		return rc;
 	}
 	wait_for_completion(&t.c);
-	if (t.task.rv < sizeof(__le32))
+	if (t.task.rv < 2 * sizeof(__le32))
 		return -EIO;
 
 	*length = le32_to_cpu(t.response_pl[1]);