drm/i915/guc: Rename GuC register state capture node to be more obvious

The GuC specific register state entry in the error capture object was
just called 'capture'. Although the companion 'node' entry was called
'guc_capture_node'. Rename the base entry to be 'guc_capture' instead
so that it is a) more consistent and b) more obvious what it is.

Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230127002842.3169194-9-John.C.Harrison@Intel.com