Add compatible string for AM64 SoC in device tree binding of OMAP I2C
modules as the same IP is used.

Signed-off-by: Aswath Govindraju <a-govindraju@ti.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Wolfram Sang <wsa@kernel.org>