drm/i915/guc: Debug print LRC state entries only if the context is pinned

After the context is unpinned the backing memory can also be unpinned,
so any accesses via the lrc_reg_state pointer can end up in unmapped
memory. To avoid that, make sure to only access that memory if the
context is pinned when printing its info.

v2: fix newline alignment

Fixes: 28ff6520 ("drm/i915/guc: Update GuC debugfs to support new GuC")
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: John Harrison <John.C.Harrison@Intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: <stable@vger.kernel.org> # v5.15+
Reviewed-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250115001334.3875347-1-daniele.ceraolospurio@intel.com