[PATCH] powerpc: Remove dregs of bootinfo.h

Since I sent the patch to purge bootinfo.h from ARCH=powerpc and
ARCH=ppc64, setup-common.c has come into existence, and another
#include of bootinfo.h slipped in.  This patch removes it.  It also
removes include/asm-ppc64/bootinfo.h, which somehow survived the
previous patch which was supposed to remove it.

Signed-off-by: Paul Mackerras <paulus@samba.org>