powerpc/85xx: verify the current address of CCSR before relocating it

Verify that CCSR is actually located where it is supposed to be before
we relocate it.  This is useful in detecting U-Boot configurations that
are broken (e.g. an incorrect value for CONFIG_SYS_CCSRBAR_DEFAULT).
If the current value is wrong, we enter an infinite loop, which is handy
for debuggers.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>