drm/vc4: hvs: Print error if we fail an allocation

We need to allocate a few additional structures when checking our
atomic_state, especially related to hardware SRAM that will hold the
plane descriptors (DLIST) and the current line context (LBM) during
composition.

Since those allocation can fail, let's add some error message in that
case to help debug what goes wrong.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>