i2c: omap: bus: add a receiver flag

that way we can ignore TX IRQs while in receiver
mode and ignore RX IRQs while in transmitter mode.

Signed-off-by: Felipe Balbi <balbi@ti.com>
[Remove unnecessary braces]
Signed-off-by: Shubhrajyoti D <shubhrajyoti@ti.com>
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>