nvmem: sunxi_sid: Always use 32-bit MMIO reads

The SID SRAM on at least some SoCs (A64 and D1) returns different values
when read with bus cycles narrower than 32 bits. This is not immediately
obvious, because memcpy_fromio() uses word-size accesses as long as
enough data is being copied.

The vendor driver always uses 32-bit MMIO reads, so do the same here.
This is faster than the register-based method, which is currently used
as a workaround on A64. And it fixes the values returned on D1, where
the SRAM method was being used.

The special case for the last word is needed to maintain .word_size == 1
for sysfs ABI compatibility, as noted previously in commit de2a3eae
("nvmem: sunxi_sid: Optimize register read-out method").

Fixes: 07ae4fde

 ("nvmem: sunxi_sid: Add support for D1 variant")
Cc: stable@vger.kernel.org
Tested-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20230127104015.23839-3-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>