Staging: comedi: comedi_fops: Remove unused stat.h header

Unused after commit 6e302939 ("staging: comedi: comedi_fops:
coding style fixes") - Fixed coding style in comedi_fops.c
Symbolic to octal permission.

Anyway it's included in module.h

Signed-off-by: Cheah Kok Cheong <thrust73@gmail.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>