powerpc/boot: Change the WARN to INFO for boot wrapper overlap message

commit c55aef0e5bc6 ("powerpc/boot: Change the load address
for the wrapper to fit the kernel") introduced a WARNING to
inform the user that the uncompressed kernel would overlap
the boot uncompressing wrapper code. Change it to an INFO.

I initially thought, this would be a 'WARNING' for the those
boards, where the link_address should be fixed, so that the
user can take actions accordingly.

Changing the same to INFO.

Signed-off-by: Suzuki K. Poulose <suzuki@in.ibm.com>
Signed-off-by: Josh Boyer <jwboyer@gmail.com>