Fix initrd/dtb interaction

The original code would wrongly relocate the blob to be right before
the initrd if it existed.  The blob *must* be within CFG_BOOTMAPSZ,
if it is defined.  So we make two changes:

1) flag the blob for relocation whenever its address is above BOOTMAPSZ

2) If the blob is being relocated, relocate it before kbd, not initrd

Signed-off-by: Andy Fleming <afleming@freescale.com>