drm/drm_dp_helper: Fix spelling issue and add missing description for 'enable_frl_ready_hpd'

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/drm_dp_helper.c:965: warning: Function parameter or member 'color_spc' not described in 'drm_dp_downstream_rgb_to_ycbcr_conversion'
 drivers/gpu/drm/drm_dp_helper.c:965: warning: Excess function parameter 'colorspc' description in 'drm_dp_downstream_rgb_to_ycbcr_conversion'
 drivers/gpu/drm/drm_dp_helper.c:2678: warning: Function parameter or member 'enable_frl_ready_hpd' not described in 'drm_dp_pcon_frl_prepare'

Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210115181601.3432599-14-lee.jones@linaro.org

drivers/gpu/drm/drm_dp_helper.c

@@ -954,7 +954,7 @@ EXPORT_SYMBOL(drm_dp_downstream_444_to_420_conversion);
  *                                               RGB->YCbCr conversion capability
  * @dpcd: DisplayPort configuration data
  * @port_cap: downstream facing port capabilities
- * @colorspc: Colorspace for which conversion cap is sought
+ * @color_spc: Colorspace for which conversion cap is sought
  *
  * Returns: whether the downstream facing port can convert RGB->YCbCr for a given
  * colorspace.
@@ -2671,6 +2671,7 @@ EXPORT_SYMBOL(drm_dp_get_pcon_max_frl_bw);
 /**
  * drm_dp_pcon_frl_prepare() - Prepare PCON for FRL.
  * @aux: DisplayPort AUX channel
+ * @enable_frl_ready_hpd: Configure DP_PCON_ENABLE_HPD_READY.
  *
  * Returns 0 if success, else returns negative error code.
  */