arm64: dts: X-Gene v2: I2C1 clock is always on

X-Gene v2 I2C0 and I2C1 controllers share the same clock
enable register field. This patch remove clock node for I2C1
and leave I2C1 clock always on as having it toggled on/off
will affect I2C0 operation.

Signed-off-by: Duc Dang <dhdang@apm.com>