Check early whether device registers can be accessed. Some BIOSes have
a broken security policy that prevents access to the device registers,
and return values from ioread() can be misinterpreted. If a read of
a feature register returns a -1, we may not be able to access
any device register, so report the problem and suggestion, and return.

For the PSP, the feature register is checked. For the CCP, the queue
register is checked.
Signed-off-by: Gary R Hook <gary.hook@amd.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>