EmbeddedPkg/Lan9118Dxe: minor DEBUG tidyup

EmbeddedPkg/Lan9118Dxe: minor DEBUG tidyup

This patch makes a few minor DEBUG output changes:

- Fix typo in DEBUG output: Negociation->Negotiation

- Change DEBUG occurrences of "Lan9118" to "LAN9118" to make grepping
  the log output easier.

- Change the warning that auto-negotiation is not supported when
  AutoNegotiate() returns an error.
  The function already reports if the feature is supported or not and
  can also return an error for other reasons.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ryan Harkin <ryan.harkin@linaro.org>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>