net/davinci_emac: use devres APIs

Use devres APIs where possible to simplify error handling
in driver probe.

While at it, also rename the goto targets in error path to
introduce some consistency in how they are named.

Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>