mmc: rockchip_dw_mmc: Allow 4-bit mode when 8-bit mode is supported

mmc: rockchip_dw_mmc: Allow 4-bit mode when 8-bit mode is supported

Hosts capable of 8-bit can also do 4 bits, fix use of 4-bit mode when
8-bit mode is supported.

This fixes use of 1-bit mode with SD NAND on ROCK Pi S using the DT in
v6.11-rc1 that chage to use 8-bit bus to also support eMMC. With this
4-bit mode is used with SD NAND and 8-bit mode with eMMC, same as in
Linux kernel.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>