PCI/ACPI: Rename _HPX structs from hpp_* to hpx_*

PCI/ACPI: Rename _HPX structs from hpp_* to hpx_*

The names of the hpp_type0, hpp_type1 and hpp_type2 structs suggest that
they're related to _HPP, when in fact they're related to _HPX.

The struct hpp_type0 denotes an _HPX Type 0 setting record that supersedes
the _HPP setting record, and it has been used interchangeably for _HPP as
per the ACPI specification (see version 6.3, section 6.2.9.1) which states
that it should be applied to PCI, PCI-X and PCI Express devices, with
settings being ignored if they are not applicable.

Rename them to hpx_type0, hpx_type1 and hpx_type2 to reflect their relation
to _HPX rather than _HPP.

Link: https://lore.kernel.org/r/20190827094951.10613-2-kw@linux.com
Signed-off-by: Krzysztof Wilczynski <kw@linux.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>