drm/i915: Introduce concept of a sub-platform

drm/i915: Introduce concept of a sub-platform

Concept of a sub-platform already exist in our code (like ULX and ULT
platform variants and similar),implemented via the macros which check a
list of device ids to determine a match.

With this patch we consolidate device ids checking into a single function
called during early driver load.

A few low bits in the platform mask are reserved for sub-platform
identification and defined as a per-platform namespace.

At the same time it future proofs the platform_mask handling by preparing
the code for easy extending, and tidies the very verbose WARN strings
generated when IS_PLATFORM macros are embedded into a WARN type
statements.

v2: Fixed IS_SUBPLATFORM. Updated commit msg.
v3: Chris was right, there is an ordering problem.

v4:
 * Catch-up with new sub-platforms.
 * Rebase for RUNTIME_INFO.
 * Drop subplatform mask union tricks and convert platform_mask to an
   array for extensibility.

v5:
 * Fix subplatform check.
 * Protect against forgetting to expand subplatform bits.
 * Remove platform enum tallying.
 * Add subplatform to error state. (Chris)
 * Drop macros and just use static inlines.
 * Remove redundant IRONLAKE_M. (Ville)

v6:
 * Split out Ironlake change.
 * Optimize subplatform check.
 * Use __always_inline. (Lucas)
 * Add platform_mask comment. (Paulo)
 * Pass stored runtime info in error capture. (Chris)

v7:
 * Rebased for new AML ULX device id.
 * Bump platform mask array size for EHL.
 * Stop mentioning device ids in intel_device_subplatform_init by using
   the trick of splitting macros i915_pciids.h. (Jani)
 * AML seems to be either a subplatform of KBL or CFL so express it like
   that.

v8:
 * Use one device id table per subplatform. (Jani)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Jose Souza <jose.souza@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190327142328.31780-1-tvrtko.ursulin@linux.intel.com