staging: et131x: Remove unnecessary defines to enable driver PM

The Power Management functions can be conditional by assigning pm ops
directly to .driver.pm, instead of using #ifdef's, saving some lines of
code.

Reported-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Mark Einon <mark.einon@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>