drm/panel: Fix build error on !CONFIG_OF

Move helpers outside of CONFIG_OF, so basic allocation also works
without it.

Fixes: ed9c594d ("drm/panel: Add new helpers for refcounted panel allocatons")
Fixes: dcba396f ("drm/panel: Add refcount support")
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Link: https://lore.kernel.org/r/nyrjnvctqnk6f3x5q7rlmy5nb7iopoti56pgh43zqknici5ms4@cibpldh7epra


Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>