ata: make PATA_PLATFORM selectable only for suitable architectures

ata: make PATA_PLATFORM selectable only for suitable architectures

It is currently possible to select "Generic platform device PATA support"
in two situations:

  - architecture allows the generic platform device PATA support and
    indicates that with "select HAVE_PATA_PLATFORM".
  - if the user claims to be an EXPERT by setting CONFIG_EXPERT to yes

However, there is no use case to have Generic platform device PATA support
in a kernel build if the architecture definition, i.e., the selection of
configs by an architecture, does not support it.

If the architecture definition is wrong, i.e., it just misses a 'select
HAVE_PATA_PLATFORM', then even an expert that configures the kernel build
should not just fix that by overruling the claimed support by an
architecture. If the architecture definition is wrong, the expert should
just provide a patch to correct the architecture definition instead---in
the end, if the user is an expert, sending a quick one-line patch should
not be an issue.

In other words, I do not see the deeper why an expert can overrule the
architecture definition in this case, as the expert may not overrule the
config selections defined by the architecture in the large majority
---or probably all other (modulo some mistakes)---of similar cases.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>