I2C: OMAP: fix FIFO usage for OMAP4

Currently the fifo depth is set to zero for OMAP4 which disables
the FIFO usage. This patch enables the FIFO usage for I2C transactions
on OMAP4 also.

Tested on omap4430 and 3430.

Tested-and-Reported-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Shubhrajyoti D <shubhrajyoti@ti.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>