e1000e: separate mutex usage between NVM and PHY/CSR register for ICHx/PCH

Accesses to NVM and PHY/CSR registers on ICHx/PCH-based parts are protected
from concurrent accesses with a mutex that is acquired when the access is
initiated and released when the access has completed.  However, the two
types of accesses should not be protected by the same mutex because the
driver may have to access the NVM while already holding the mutex over
several consecutive PHY/CSR accesses which would result in livelock.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>