i2c-omap: Program I2C_WE on OMAP4 to enable i2c wakeup

For the I2C module to be wakeup capable, programming I2C_WE register (which
was skipped for OMAP4430) is needed even on OMAP4.

This fixes i2c controller timeouts which were seen recently with the static
dependency being cleared between MPU and L4PER clockdomains.

Signed-off-by: Rajendra Nayak <rnayak@ti.com>
[ben-linux@fluff.org: re-flowed description]
Signed-off-by: Ben Dooks <ben-linux@fluff.org>