For i2c normal work, we need to slow down the bus speed. However, the
slow down breaks the eeprom firmware load. So, use normal speed for
eeprom booting and then restore the i2c speed after that.

It should also be noticed that no other I2C transfer should be in course
while booting from eeprom, otherwise, tda10046 goes into an instable
state. So, proper locking are needed at the i2c bus master.

Tested with saa7134 MSI TV @nyware A/D board, that comes with an eeprom
with firmware version 29.
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>