mpc8xx: remove RRvision board support

This board is still a non-generic board.

Unused code in arch/powerpc/cpu/mpc8xx/video.c should be also deleted
because CONFIG_VIDEO_ENCODER_AD7176, CONFIG_VIDEO_ENCODER_AD7177,
CONFIG_VIDEO_ENCODER_AD7179 are not defined any more.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Wolfgang Denk <wd@denx.de>
diff --git a/doc/README.scrapyard b/doc/README.scrapyard
index 623a30e..00a5447 100644
--- a/doc/README.scrapyard
+++ b/doc/README.scrapyard
@@ -12,6 +12,7 @@
 
 Board            Arch        CPU            Commit      Removed     Last known maintainer/contact
 =================================================================================================
+RRvision         powerpc     mpc8xx         -           -           Wolfgang Denk <wd@denx.de>
 SPD823TS         powerpc     mpc8xx         -           -           Wolfgang Denk <wd@denx.de>
 KUP4K            powerpc     mpc8xx         -           -           Klaus Heydeck <heydeck@kieback-peter.de>
 KUP4X            powerpc     mpc8xx         -           -           Klaus Heydeck <heydeck@kieback-peter.de>