staging: et131x: Remove 'reduce number of spinlocks' TODO item

The number of spinlocks has been halved, from 8 to 4 since this
comment was made, let's see if this is enough.

Signed-off-by: Mark Einon <mark.einon@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>