sunxi: armv8: fel: load only 32-bit values

Both the values and the MMIO addresses that we need during the 64-bit FEL
restore are smaller than 2^32, so we don't need to do any 64-bit loads.

Change the loads to only load 32 bits worth of data, that saves us some
bytes for storing the values.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Samuel Holland <samuel@sholland.org>
Tested-by: Samuel Holland <samuel@sholland.org>