[PATCH] g_file_storage: fix obscure race condition

This patch (as575) fixes an unlikely race in the g_file_storage driver.
The problem can occur only when the driver is unbound before its
initialization routine has finished.

I also took the opportunity to replace kmalloc/memset with kzalloc.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>