[PATCH] request_firmware(): avoid race conditions

Avoid race occurs when some process have open file descriptor for class
device attributes and already firmware allocated memory are freed.  Don't
allow negative loading timeout.

Signed-off-by: Stanislaw W. Gruszka <stf_xl@wp.pl>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>