drm/vc4: hvs: Create hw_init function

drm/vc4: hvs: Create hw_init function

Since the BCM2712 will feature a significantly different HVS, let's move
the hardware initialisation part of our bind function into a separate
function.

That way, it will be easier to extend in the future.

Signed-off-by: Maxime Ripard <mripard@kernel.org>
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240621152055.4180873-24-dave.stevenson@raspberrypi.com
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>