staging: et131x: Audit and update comments

Many of the functions and variables in the driver have been renamed and are now
more understandable, as well as defines added for various constants. Update /
remove some comments to reflect this.

Also many comments were unnecessary dialogue describing what is evident
from the code, or comments were just plain incorrect. Remove these too.
Signed-off-by: NMark Einon <mark.einon@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>