I2C: Fix mxc_i2c.c problem on imx31_phycore

I2C: Fix mxc_i2c.c problem on imx31_phycore

The problem was caused by a global variable being used early in the boot
process.

The symptoms were on imx31_phycore board, reading the environment from I2C
EEPROM didn't work correctly and causes default environment to be loaded.

Signed-off-by: Marek Vasut <[email protected]>
Cc: Wolfgang Denk <[email protected]>
Cc: Albert ARIBAUD <[email protected]>
Cc: Heiko Schocher <[email protected]>
Cc: Stefano Babic <[email protected]>
Acked-by: Heiko Schocher <[email protected]>
Tested-by: Anatolij Gustschin <[email protected]>
Tested-by: Stefano Babic <[email protected]>