CISTPL_SDIO_STD(0x91) is a known tuple, but sdio_cis don't define it, so
we get the warning below while probing several sdio wifi cards.

Refer to SDIO spec, it's not needed to parse the tuple, so this patch make
it a known one.

[    4.098980] mmc2: queuing unknown CIS tuple 0x91 (3 bytes)
[    4.099033] mmc2: new ultra high speed SDR104 SDIO card at address 0001
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>