mmc: sh_sdhi: Fix the ACMD handling

The command handling in this driver is awful, esp. because the driver
depends on command numbers to determine whether this is APPCMD or not.
Also, handling of command RSP response types is totally wrong.

This patch at least plucks out some of the custom command encoding and
fixes the APPCMD handling. The RSP handling still needs work, yet that
might not be needed as it turns out the uniphier-sd.c driver is in much
better shape and supports the same IP, so we might be able to just drop
this driver in favor of the uniphier one.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Hiroyuki Yokoyama <hiroyuki.yokoyama.vx@renesas.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
Cc: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>