Start with a clean slate before dealing with bit 16 (pointer size)
of Master Configuration Register.
This fixes the case of AArch64 boot loader + AArch32 kernel, when
the boot loader might set MCFGR[PS] and kernel would fail to clear it.

Cc: <stable@vger.kernel.org>
Reported-by: Alison Wang <alison.wang@nxp.com>
Signed-off-by: Horia Geantă <horia.geanta@nxp.com>
Reviewed-By: Alison Wang <Alison.wang@nxp.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>