drm/i915/dsi: add VLV_ prefix to VLV only register macros

All the BXT specific macros have BXT_ prefix, do the same for VLV for
consistency. This is helpful because the platform specific macros can
use the static MIPI MMIO base rather than dynamic.

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/7e101167c52746748dbff739bc9247a664ca2840.1713520813.git.jani.nikula@intel.com


Signed-off-by: Jani Nikula <jani.nikula@intel.com>