drm/print: drop include seq_file.h

Never include where a forward declaration will suffice.
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Acked-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240410141434.157908-2-jani.nikula@intel.com
Link: https://patchwork.freedesktop.org/patch/msgid/20240422121011.4133236-2-jani.nikula@intel.comSigned-off-by: Jani Nikula <jani.nikula@intel.com>

include/drm/drm_print.h

@@ -28,7 +28,6 @@
 
 #include <linux/compiler.h>
 #include <linux/printk.h>
-#include <linux/seq_file.h>
 #include <linux/device.h>
 #include <linux/dynamic_debug.h>
 
@@ -36,6 +35,7 @@
 
 struct debugfs_regset32;
 struct drm_device;
+struct seq_file;
 
 /* Do *not* use outside of drm_print.[ch]! */
 extern unsigned long __drm_debug;