drm/i915/guc: Allocate separate shared data object for GuC communication

drm/i915/guc: Allocate separate shared data object for GuC communication

We were using first page of kernel context render state for sharing data
with GuC. While it's justified by the fact that those pages are not used
(note, GuC still enforces this layout and refuses to work if we remove
the extra page in front), it's also confusing (why are we using this
particular page?). Let's allocate a separate object instead.

v2: Drop kernel_context from GuC suspend/resume action handlers (Michel)

Suggested-by: Daniele Ceraolo Spurio <[email protected]>
Signed-off-by: Michał Winiarski <[email protected]>
Cc: Chris Wilson <[email protected]>
Cc: Daniele Ceraolo Spurio <[email protected]>
Cc: Jeff McGee <[email protected]>
Cc: Michal Wajdeczko <[email protected]>
Cc: Oscar Mateo <[email protected]>
Reviewed-by: Daniele Ceraolo Spurio <[email protected]>
Signed-off-by: Chris Wilson <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]