wl12xx: 1281/1283 support - Add acx commands

New acx command that sets: Rx fifo enable reduced bus transactions
in RX path. Tx bus transactions padding to SDIO block size that
improve preference in Tx and essential for working with SDIO HS (48Mhz).
The max SDIO block size is 256 when working with Tx bus transactions
padding to SDIO block.

Add new ops to SDIO & SPI that handles the win size change in case of
transactions padding (relevant only for SDIO).

[Fix endianess issues; simplify sdio-specific block_size handling;
minor changes in comments; use "aligned_len" in one calculation
instead of "pad" to avoid confusion -- Luca]

Signed-off-by: Shahar Levi <shahar_levi@ti.com>
Reviewed-by: Luciano Coelho <coelho@ti.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>