drm/i915: Add missing forward declarations/includes to display power headers

Add the seq_file struct forward declaration to intel_display_power.h
fixing the build error below. While at it add the rest of missing
forward declarations/includes to the display power header files.

In file included from <command-line>:
./../drivers/gpu/drm/i915/display/intel_display_power.h:255:70: error: 'struct seq_file'
declared inside parameter list will not be visible outside of this definition or declaration [-Werror]
  255 | void intel_display_power_debug(struct drm_i915_private *i915, struct seq_file *m);
      |                                                                      ^~~~~~~~

Closes: https://lore.kernel.org/intel-gfx/[email protected]/
Reported-by: Randy Dunlap <[email protected]>
Acked-by: Randy Dunlap <[email protected]>
Tested-by: Randy Dunlap <[email protected]> # build-tested
Reviewed-by: Jouni Högander <[email protected]>
Signed-off-by: Imre Deak <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

0 files changed, 0 insertions, 0 deletions