drm/i915: remove unused pipe/plane B register macros

None of these are used. The parametrized register macros all depend on
the pipe/plane A offset macros alone. Remove the unused ones.

v2: Rebase

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/16d278bea466a69cdce94fd83d98dd15ce1a8c89.1717773890.git.jani.nikula@intel.com


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