I2C: OMAP: Fix the interrupt clearing in OMAP4

On OMAP4 we were writing 1 to IRQENABLE_CLR which cleared only
the arbitration lost interrupt. The patch intends to fix the same by writing 0
to the IE register clearing all interrupts.

This is based on the work done by Vikram Pandita <vikram.pandita@ti.com>.

The  changes from the original patch ...
-  Does not use the IRQENABLE_CLR register to clear as it is not mentioned
  to be legacy register IRQENABLE_CLR helps in  atomically
  setting/clearing specific interrupts, instead use the OMAP_I2C_IE_REG as we
  are clearing all interrupts.

Cc: Vikram Pandita <vikram.pandita@ti.com>
Reviewed-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Shubhrajyoti D <shubhrajyoti@ti.com>
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>