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Prior to this commit, excuting this code:

    i2c = I2C(1, I2C.CONTROLLER, dma=True)
    i2c.send(data, addr=i2c_addr)

the call to i2c.send() does not return and the board needs a reset.  This
code works when dma=False.

According to the specification, I2Cx_EV_IRQHandler should:
- Write DR to address when Start condition generated.
- Clear ADDR by reading SR2 after reading SR2 when address sent.

These processes are included in HAL_I2C_EV_IRQHandler(), however the
firmware size increses about 2KB if HAL_I2C_EV_IRQHandler is called.  This
commit adds above processes to i2c_ev_irq_handler, and increases firmware
by less than 100 bytes.

Fixes issue #2643.