i2c: mediatek: Disable i2c start_en and clear intr_stat brfore reset

The i2c controller driver do dma reset after transfer timeout,
but sometimes dma reset will trigger an unexpected DMA_ERR irq.
It will cause the i2c controller to continuously send interrupts
to the system and cause soft lock-up. So we need to disable i2c
start_en and clear intr_stat to stop i2c controller before dma
reset when transfer timeout.

Fixes: aafced67

("i2c: mediatek: move dma reset before i2c reset")
Signed-off-by: Qii Wang <qii.wang@mediatek.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>