We can now process any RAS EEPROM address from
VBIOS. Generalize so as to compute the top three
bits of the 19-bit EEPROM address, from any byte
returned as the "i2c address" from VBIOS.

Cc: John Clements <john.clements@amd.com>
Cc: Hawking Zhang <Hawking.Zhang@amd.com>
Cc: Alex Deucher <Alexander.Deucher@amd.com>
Signed-off-by: Luben Tuikov <luben.tuikov@amd.com>
Reviewed-by: Alex Deucher <Alexander.Deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>