dt-bindings: i2c: nvidia,tegra20-i2c: combine same if:then: clauses

"if:then:" block for Tegra114 and Tegra120 I2C controllers has the same
"then" part (same clocks), so combine them.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>