net: qcom/emac: disable interrupts before calling phy_disconnect

There is a race condition that can occur if EMAC interrupts are
enabled when phy_disconnect() is called.  phy_disconnect() sets
adjust_link to NULL.  When an interrupt occurs, the ISR might
call phy_mac_interrupt(), which wakes up the workqueue function
phy_state_machine().  This function might reference adjust_link,
thereby causing a null pointer exception.

Signed-off-by: Timur Tabi <timur@codeaurora.org>
Signed-off-by: David S. Miller <davem@davemloft.net>