i2c: nomadik: support >=1MHz speed modes

i2c: nomadik: support >=1MHz speed modes

 - BRCR value must go into the BRCR1 field when in high-speed mode.
   It goes into BRCR2 otherwise.

 - Remove fallback to standard mode if priv->sm > I2C_FREQ_MODE_FAST.

 - Set SM properly in probe; previously it only checked STANDARD versus
   FAST. Now we set STANDARD, FAST, FAST_PLUS or HIGH_SPEED.

 - Remove all comment sections saying we only support low-speeds.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>