pinctrl: sunxi: Avoid using .bss for SPL

sunxi platforms put .bss in DRAM, so .bss is not available in SPL before
DRAM controller initialization. Therefore, this buffer must be placed in
the .data section.

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