i2c/isp1301_omap: Convert to a new-style i2c driver, part 2

Based on David Brownell's patch for tps65010 and previous work by
Felipe Balbi, this patch finishes conversting isp1301_omap to a
new-style i2c driver.

There's definitely room for further drivers cleanups, but these are
out of the scope of this patch.

Signed-off-by: Jean Delvare <khali@linux-fr.org>