PowerPC: drop some 74xx_7xx boards and related code

The file  board/Marvell/include/mv_gen_reg.h  is incompatible with
the GPL (see for example the "MARVELL RESERVES THE RIGHT AT ITS SOLE
DISCRETION TO REQUEST THAT THIS CODE BE IMMEDIATELY RETURNED TO
MARVELL" clause).  As this cannot be fixed, we remove the file and all
code that depends on it.  Fortunately this only affects some very old
boards that have long reached EOL:
	CPCI750
	DB64360
	DB64460
	p3m750
	p3m7448

Signed-off-by: Wolfgang Denk <wd@denx.de>
Cc: Reinhard Arlt <reinhard.arlt@esd-electronics.com>
Cc: Stefan Roese <sr@denx.de>
Cc: Roger Meier <r.meier@siemens.com>
diff --git a/doc/README.scrapyard b/doc/README.scrapyard
index 1b6ae83..7e5db20 100644
--- a/doc/README.scrapyard
+++ b/doc/README.scrapyard
@@ -12,6 +12,11 @@
 
 Board            Arch        CPU            Commit      Removed     Last known maintainer/contact
 =================================================================================================
+CPCI750		 powerpc     74xx_7xx	    -		-	    Reinhard Arlt <reinhard.arlt@esd-electronics.com>
+DB64360		 powerpc     74xx_7xx	    -		-
+DB64460		 powerpc     74xx_7xx	    -		-
+p3m750		 powerpc     74xx_7xx	    -		-	    Stefan Roese <sr@denx.de>
+p3m7448		 powerpc     74xx_7xx	    -		-	    Stefan Roese <sr@denx.de>
 MVBC_P           powerpc     mpc5xxx        af55e35	2014-10-10  Andre Schwarz <andre.schwarz@matrix-vision.de>
 MVSMR            powerpc     mpc5xxx        af55e35	2014-10-10  Andre Schwarz <andre.schwarz@matrix-vision.de>
 MERGERBOX        powerpc     mpc83xx        e7a5656	2014-10-10  Andre Schwarz <andre.schwarz@matrix-vision.de>