drm/i915: Use enum pipe consistently

Replace all "int pipe"s with "enum pipe pipe"s to make it clear
what we're dealing with.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190821173033.24123-3-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -376,7 +376,7 @@ static int i915_gem_object_info(struct seq_file *m, void *data)
 static void gen8_display_interrupt_info(struct seq_file *m)
 {
 	struct drm_i915_private *dev_priv = node_to_i915(m->private);
-	int pipe;
+	enum pipe pipe;
 
 	for_each_pipe(dev_priv, pipe) {
 		enum intel_display_power_domain power_domain;