drm/vc4: change vc4_dma_range_matches from a global to static

sparse reports
drivers/gpu/drm/vc4/vc4_drv.c:270:27: warning: symbol 'vc4_dma_range_matches' was not declared. Should it be static?

vc4_dma_range_matches is only used in vc4_drv.c, so it's storage class specifier
should be static.

Fixes: da8e393e

 ("drm/vc4: drv: Adopt the dma configuration from the HVS or V3D component")
Signed-off-by: Tom Rix <trix@redhat.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20220629200101.498138-1-trix@redhat.com