net: Multiple updates/enhancements to designware.c

This patch adds the following changes to designware ethernet driver
found on the ST SPEAr SoC:

- Don't init MAC & PHY upon startup. This causes a delay, waiting for
  the auto negotiation to complete. And we don't want this delay to
  always happen. Especially not on platforms where ethernet is not
  used at all (e.g. booting via flash).
  Instead postpone the MAC / PHY configuration to the stage, where
  ethernet is first used.
- Add possibility for board specific PHY init code. This is needed
  for example on the X600 board, where the Vitesse PHY needs to be
  configured for GMII mode.
  This board specific PHY init is done via the function
  designware_board_phy_init(). And this driver now adds a weak default
  which can be overridden by board code.
- Use common functions miiphy_speed() & miiphy_duplex() to read
  link status from PHY.
- Print status and progress of auto negotiation.
- Print link status (speed, dupex) upon first usage.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Amit Virdi <amit.virdi@st.com>
Cc: Vipin Kumar <vipin.kumar@st.com>
Cc: Joe Hershberger <joe.hershberger@gmail.com>
Acked-by: Joe Hershberger <joe.hershberger@gmail.com>