drm/i915: Fix intel_psr_init() kerneldoc

In commit c39055b0 ("drm/i915: Pass dev_priv to
intel_setup_outputs()"), I forgot to update the kerneldoc for
intel_psr_init() init, leading to warnings when building the
documentation:

    drivers/gpu/drm/i915/intel_psr.c:822: warning: No description found for parameter 'dev_priv'
    drivers/gpu/drm/i915/intel_psr.c:822: warning: Excess function parameter 'dev' description in 'intel_psr_init'

Fixes: c39055b0 ("drm/i915: Pass dev_priv to intel_setup_outputs()")
Cc: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: intel-gfx@lists.freedesktop.org
Signed-off-by: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1480420127-11382-1-git-send-email-ander.conselvan.de.oliveira@intel.com