fsl: simplify the "mac id" command, improve boot-time informational message

The "mac id" command took a 4-character parameter as the identifier string.
However, for any given board, only one kind of identifier is acceptable, so it
makes no sense to ask the user to type it in.  Instead, if the user enters
"mac id", the identifier (and also the version, if it's NXID) will
automatically be set to the correct value.

Improve the message that is displayed when EEPROM is read during boot.  It now
displays "EEPROM:" and then either an error message or the EEPROM identifier
if successful.

If the identifier in EEPROM is valid, then always reject a bad CRC, even if the
CRC field has not been initialized.

Don't force the MAC address count to MAX_NUM_PORTS or less.  Forcing the value
to be changed resulting in an in-memory copy that does not match what's in
hardware, even though the user did not request that change.

Finally, always update the CRC value in the in-memory copy after any field
is changed, so that the CRC is always correct.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>