dts: npcx: fix i2c label prefix

i2c_shell uses "I2C_" label prefix to get the device. However, NPCX
uses controller-port architecture. Users should access the ports
instead of the controllers. Change I2C_CTRLX & I2CX_PORTX to I2CCTRL_X
& I2C_X_PORT_X to guarantee i2c_shell could get the correct device by
autocomplete.

Signed-off-by: Wealian Liao <WHLIAO@nuvoton.com>