drm/xe: Define all possible engines in media IP descriptors

Rather than trying to identify exactly which engines are available on
each platform in the IP descriptor, just include the list of all media
engines that the IP could theoretically support (i.e., 8 VCS + 4 VECS).
We still rely on the media fuse registers to tell us which specific
engine instances are actually present on a given platform, so there
shouldn't be any functional change.  This will help prevent mistakes
with engine numbering (for example ambiguity about whether the 2nd VCS
engine on a platform with exactly two engines is numbered "VCS1" or
"VCS2") and will also future-proof the code a bit more in case new SKUs
or platform refreshes extend the engine list in the future.

Note that the media fuse register technically has an 8-bit field for
VECS engine presence starting on Xe2.  However there's still no MMIO
register range reserved for VE engines above VECS3, so VE0-VE3 is still
consider the "maximum" VE engine mask that the driver can support for
now.

Bspec: 52614, 52615, 62567
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240417152621.3357990-2-matthew.d.roper@intel.com