u-boot-fslc: Disable I2C for mx28evk to fix SGTL5000

u-boot-fslc: Disable I2C for mx28evk to fix SGTL5000

When loading a Freescale 2.6.35 on a mx28evk the following issue is
seen:

sgtl5000_hw_read: read reg error : Reg 0x00 Device with ID register 0
is not a SGTL5000

Disabling CONFIG_CMD_I2C makes the sgtl5000 probe to succeed.

Mainline kernel does not show this problem.

Until the real cause is not identified, disable 'CONFIG_CMD_I2C' for
the time being.

Change-Id: I1c79a6f7567611ce846383686481fbf923ed3434
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>