sdio: allow non-standard SDIO cards

sdio: allow non-standard SDIO cards

There are some chips (like TI WL12xx series) that can be interfaced
over SDIO but don't support the SDIO specification, meaning that they
are missing CIA (Common I/O Area) with all it's registers. Current
Linux SDIO implementation relies on those registers to identify and
configure the card, so non-standard cards can not function and cause
lots of warning from the core when it reads invalid data from
non-existent registers.

After this patch, init_card() host callback can now set new quirk
MMC_QUIRK_NONSTD_SDIO, which means that SDIO core should not try to
access any standard SDIO registers and rely on init_card() to fill all
SDIO structures instead. As those cards are usually embedded chips,
all the required information can be obtained from machine board files
by the host driver when it's called through init_card() callback.

Signed-off-by: Grazvydas Ignotas <notasas@gmail.com>