sdio: add new function for RAW (Read after Write) operation

SDIO specification allows RAW (Read after Write) operation using
IO_RW_DIRECT command (CMD52) by setting the RAW bit.  This operation is
similar to ordinary read/write commands, except that both write and read
are performed using single command/response pair.  The Linux SDIO layer
already supports this internaly, only external function is missing for
drivers to make use, which is added by this patch.

This type of command is required to implement proper power save mode
support in wl1251 wifi driver.

Android has similar patch for G1 in it's tree for the same reason:

http://android.git.kernel.org/?p=kernel/common.git;a=commitdiff;h=74a47786f6ecbe6c1cf9fb15efe6a968451deb52

Signed-off-by: Grazvydas Ignotas <notasas@gmail.com>
Acked-by: Kalle Valo <kalle.valo@iki.fi>
Cc: Dmitry Shmidt <dimitrysh@google.com>
Cc: <linux-mmc@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>