drm/i915/perf: fix gen11 engine class shift

Use the correct engine class shift value while storing the ctx hw id.
Fixes the copy+paste error from commit 61d5676b ("drm/i915/perf: fix
ctx_id read with GuC & ICL").

Apologies for not spotting this in the original review, the
specific_ctx_id_mask is correct, only the specific_ctx_id had this
problem.

v2: Just use the upper 32 bits of lrc_desc (Chris)
v3: If we use the lrc_desc, we must apply the ctx_id_mask too (Lionel)

Fixes: 61d5676b ("drm/i915/perf: fix ctx_id read with GuC & ICL")
Signed-off-by: Michel Thierry <michel.thierry@intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michel Thierry <michel.thierry@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: intel-gfx@lists.freedesktop.org
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180604233250.609-2-michel.thierry@intel.com