drm/i915/kbl: Fix revision ID checks

We usually assume that increasing PCI device revision ID's translates to
newer steppings; macros like IS_KBL_REVID() that we use rely on this
behavior.  Unfortunately this turns out to not be true on KBL; the
newer device 2 revision ID's sometimes go backward to older steppings.
The situation is further complicated by different GT and display
steppings associated with each revision ID.

Let's work around this by providing a table to map the revision ID to
specific GT and display steppings, and then perform our comparisons on
the mapped values.

v2:
 - Move the kbl_revids[] array to intel_workarounds.c to avoid compiler
   warnings about an unused variable in files that don't call the
   macros (kernel test robot).

Bspec: 18329
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200811032105.2819370-1-matthew.d.roper@intel.com
Reviewed-by: Swathi Dhanavanthri <swathi.dhanavanthri@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>