Coldfire: M5271EVB: Remove usage of CONFIG_SYS_FECI2C

Discontinue the use of CONFIG_SYS_FECI2C (only used by M5271EVB).
Use read-modify-write to activate the FEC pins without disabling I2C.

Signed-off-by: Richard Retanubun <RichardRetanubun@RuggedCom.com>