drivers: dm8806: smi bus error check

SMI bus error check mechanism is preventing the host SMI bus to be
interferred by noise on board level. Current implementation is checking
if data which is writing to/reading from the PHY has correct CRC sum.
If not, then writing/rading process is repeated by the number of
attempts defined in the KConfig. If repeating transmission will fail
by the numbers of ettemps defined in KConfing, drivers returns an
error.

Signed-off-by: Robert Slawinski <robert.slawinski1@gmail.com>