drm/i915/hdcp: fix intel_hdcp_get_repeater_ctl() error return value

intel_hdcp_get_repeater_ctl() is supposed to return unsigned register
contents. Returning negative error values is unexpected, and none of the
callers check for that.

Sort of fix the error cases by returning 0. I don't think we should hit
these cases anyway, and using 0 for the registers is safer than
0xffffffea (-EINVAL).
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231219104746.1065431-2-jani.nikula@intel.com

drivers/gpu/drm/i915/display/intel_hdcp.c

@@ -347,7 +347,7 @@ u32 intel_hdcp_get_repeater_ctl(struct drm_i915_private *i915,
 		default:
 			drm_err(&i915->drm, "Unknown transcoder %d\n",
 				cpu_transcoder);
-			return -EINVAL;
+			return 0;
 		}
 	}
 
@@ -364,7 +364,7 @@ u32 intel_hdcp_get_repeater_ctl(struct drm_i915_private *i915,
 		return HDCP_DDIE_REP_PRESENT | HDCP_DDIE_SHA1_M0;
 	default:
 		drm_err(&i915->drm, "Unknown port %d\n", port);
-		return -EINVAL;
+		return 0;
 	}
 }