mxc_i2c: combine i2c_imx_bus_busy and i2c_imx_trx_complete into wait_for_sr_state

Not using udelay gives a more accurate timeout. The current implementation of udelay
in imx-common does not seem to wait at all for a udelay(1).

Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>
Acked-by: Marek Vasut <marex@denx.de>

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V2: Added WATCHDOG_RESET as suggested by Marek Vasut
add error message when stop fails

mxc_i2c: code i2c_probe as a 0 length i2c_write

Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>
Acked-by: Marek Vasut <marex@denx.de>
Acked-by: Stefano Babic <sbabic@denx.de>