stmmac: fix concurrency in eee initialization.

This patch aims to fix the concurrency in eee initialization
inside the stmmac driver and related warnings when enable
DEBUG_ATOMIC_SLEEP.

Prior this patch, the stmmac_eee_init could be called in several places
as shown below:

stmmac_open  stmmac_resume         PHY Layer
    |            |                     |
  stmmac_hw_setup           stmmac_adjust_link
    |                                  |           stmmac ethtool
    |__________________________|______________|
                                       |
                                 stmmac_eee_init

The patch removes the stmmac_eee_init call inside the stmmac_hw_setup
that is unnecessary. It is sufficient to call it in the adjust_link to
always guarantee that EEE is always configured at mac level too.

Fixing the lock protection now it is covered another case (not
considered before). The stmmac_eee_init could be called by the ethtool
so critical sections must be protected inside this function too.

Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>