ARM: socfpga: Assure correct CPACR configuration

Make sure the ARM CPACR register is zeroed out, this is mandatory
on Arria10.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Chin Liang See <chin.liang.see@intel.com>
Cc: Dinh Nguyen <dinguyen@kernel.org>