[PATCH] ide: Fix crash on repeated reset

Michal Miroslaw reported a problem (bugzilla #7023) where a user initiated
reset while the IDE layer was already resetting the channel caused a crash,
and provided a rough fix.

This is a slightly cleaner version of the fix which tracks the reset state
and blocks further reset requests while a reset is in progress.

Note this is not a security issue - random end users can't access the
ioctl in question anyway.

Signed-off-by: Alan Cox <alan@redhat.com>
Cc: Michal Miroslaw <mirq-linux@rere.qmqm.pl>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>