drm/bridge/synopsys: remove commented-out flag in Makefile

Please do not comment out unneeded code.  Remove.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1532496348-11589-1-git-send-email-yamada.masahiro@socionext.com