I2C: mxc_i2c rework

I2C: mxc_i2c rework

Rewrite the mxc_i2c driver.
 * This version is much closer to Linux implementation.
 * Fixes IPG_PERCLK being incorrectly used as clock source
 * Fixes behaviour of the driver on iMX51
 * Clean up coding style a bit ;-)

Signed-off-by: Marek Vasut <[email protected]>
Cc: Stefano Babic <[email protected]>
Cc: Heiko Schocher <[email protected]>
Cc: Jason Hui <[email protected]>
Acked-by: Jason Liu <[email protected]>
Acked-by: Heiko Schocher <[email protected]>
Tested-by: Jason Liu <[email protected]>