[PATCH] mmc: use own work queue

The MMC layer uses the standard work queue for doing card detection.  As this
queue is shared with other crucial subsystems, the effects of a long (and
perhaps buggy) detection can cause the system to be unusable.  E.g.  the
keyboard stops working while the detection routine is running.

The solution is to add a specific mmc work queue to run the detection code in.
This is similar to how other subsystems handle detection (a full kernel
thread is the most common theme).

Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>