i2c: pxa: keep i2c irq ON in suspend

During suspend there may still be some i2c access happening, as the
interrupt is shared between multiple drivers.
And if we don't keep i2c irq ON, there may be i2c access timeout if
i2c is in irq mode of operation.

Signed-off-by: Raul Xiong <xjian@marvell.com>
Signed-off-by: Xiaofan Tian <tianxf@marvell.com>
[vaibhav.hiremath@linaro.org: updated Changelog]
Signed-off-by: Vaibhav Hiremath <vaibhav.hiremath@linaro.org>
Cc: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>