drm/i915: Sanitycheck PCI BARs

For proper operation of i915 we need usable PCI GTTMMADDR BAR 0
(1 for GEN2). In most cases we also need usable PCI GFXMEM BAR 2.
Let's add functions to check if BARs are set, and that it have
a size greater than 0.
In case GTTMMADDR BAR, let's validate at the beginning of i915
initialization.
For other BARs, let's validate before first use.

Signed-off-by: Piotr Piórkowski <piotr.piorkowski@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220805155959.1983584-3-piotr.piorkowski@intel.com

drm/i915/pci: rename functions to have i915_pci prefix

Follow the usual naming conventions. While at it, fix i915_pci.h SPDX
license comment format and add header include guards.

Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210825150623.28980-1-jani.nikula@intel.com

drm/i915: Extract i915_module.c

The module init code is somewhat misplaced in i915_pci.c, since it
needs to pull in init/exit functions from every part of the driver and
pollutes the include list a lot.

Extract an i915_module.c file which pulls all the bits together, and
allows us to massively trim the include list of i915_pci.c.

The downside is that have to drop the error path check Jason added to
catch when we set up the pci driver too early. I think that risk is
acceptable for this pretty nice include.

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Cc: Jason Ekstrand <jason@jlekstrand.net>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210727121037.2041102-11-daniel.vetter@ffwll.ch