i2c: versatile: Add Device Tree support

This patch adds Device Tree binding ("arm,versatile-i2c") and
basic support (bus population) to versatile-i2c driver.

Signed-off-by: Pawel Moll <pawel.moll@arm.com>

[wsa: constified match-table]

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