SPI: SPL: sunxi: fix 64-bit build

SPI: SPL: sunxi: fix 64-bit build

Addresses passed on to readl and writel are expected to be of the same
size as a pointer. Change the parameter types of sunxi_spi0_read_data()
to make the compiler happy and allow a warning-free aarch64 compile.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>