dts: bindings: Rename compatible infineon,xmc4-i2c->infineon,xmc4xxx-i2c

To be consistent with other xmc4xxx drivers.

A few other device tree changes:
- Rename clock signal option as it's handled by DX1.
- Remove clock-frequency option as it's already added in
  i2c-controller.yaml, and interrupts is already defined as array
  in base.yaml.

Signed-off-by: Andriy Gelman <andriy.gelman@gmail.com>