drm/i915: Stop whitelisting CS_CTX_TIMESTAMP on Xe_HP platforms

Xe_HP architecture already makes the CS_CTX_TIMESTAMP readable by
userspace on all engines; there's no longer a need to add it to the
software-managed whitelist for the non-RCS engines.

Bspec: 45545
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Acked-by: Gustavo Sousa <gustavo.sousa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230224002300.3578985-2-matthew.d.roper@intel.com