i2c: i2c-sh_mobile: optimize ICCH/ICCL values according to I2C bus speed

ICCH/ICCL values is supposed to be calculated/optimized to strictly meet
the timing specs required by the I2C standard. The resulting I2C bus
speed does not matter at all, if it's less than 100 or 400 kHz.

With this change, sh_mobile_i2c_icch() is virtually identical to
sh_mobile_i2c_iccl(), but they're providing good descriptions of
SH-/R-Mobile I2C hardware spec, and I'd leave them as separated.

Also fix a typo in the comment, print icch/iccl values at probe, etc.

Signed-off-by: Shinya Kuribayashi <shinya.kuribayashi.px@renesas.com>

[wsa: squashed two patches for bisectability]

Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>