drm/nouveau/nvfw/acr: set wpr_generic_header_dump storage-class-specifier to static

drm/nouveau/nvfw/acr: set wpr_generic_header_dump storage-class-specifier to static

gcc with W=1 reports
drivers/gpu/drm/nouveau/nvkm/nvfw/acr.c:49:1: error: no previous
  prototype for ‘wpr_generic_header_dump’ [-Werror=missing-prototypes]
   49 | wpr_generic_header_dump(struct nvkm_subdev *subdev,
      | ^~~~~~~~~~~~~~~~~~~~~~~

wpr_generic_header_dump is only used in acr.c, so it should be static

Signed-off-by: Tom Rix <[email protected]>
Reviewed-by: Karol Herbst <[email protected]>
Signed-off-by: Karol Herbst <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]