linux-imx

enetc: WA for MDIO register access issue

Due to a hardware issue access to MDIO registers concurrent with other
ENETC register access may lead to the MDIO access being dropped or
corrupted.  The workaround introduces locking for all register access in
ENETC space.  To reduce performance impact, code except MDIO uses per-cpu
locks, MDIO code having to acquire all per-CPU locks to perform an access.
To further reduce the performance impact, datapath functions acquire the
per-cpu lock fewer times and use _hot accessors.  All the rest of the code
uses the _wa accessors which lock every time a register is accessed.

Signed-off-by: Alex Marginean <alexandru.marginean@nxp.com>