drm/xe/guc: Introduce the GuC Buffer Cache

The purpose of the GuC Buffer Cache is to maintain a set ofreusable
buffers that could be used while sending some of the CTB H2G actions
that require separate buffer with indirect data. Currently only few
PF actions need this so initialize it only when running as a PF.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241220194205.995-9-michal.wajdeczko@intel.com