drm: Silence some sparse warnings

drivers/gpu/drm/drm_pci.c:155:5: warning: symbol 'drm_pci_set_busid' was not declared. Should it be static?
drivers/gpu/drm/drm_pci.c:197:5: warning: symbol 'drm_pci_set_unique' was not declared. Should it be static?
drivers/gpu/drm/drm_pci.c:269:5: warning: symbol 'drm_pci_agp_init' was not declared. Should it be static?

drivers/gpu/drm/drm_crtc.c:181:1: warning: symbol 'drm_get_dirty_info_name' was not declared. Should it be static?
drivers/gpu/drm/drm_crtc.c:1123:5: warning: symbol 'drm_mode_group_init' was not declared. Should it be static?

drivers/gpu/drm/drm_modes.c:918:6: warning: symbol 'drm_mode_validate_clocks' was not declared. Should it be static?

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>