From IOMUX tool:
You can see that when using pin muxing options above, ECSPI1 signals belong to NVCC_EIM0 power group, ECSPI2 signals to NVCC_EIM1 and ECSPI3 to NVCC_LCD. Datasheet specifies voltage range for these power groups, which for EIM0, EIM1 and LCD are from 1.65V up to 3.6V, with typical values of 1.8V, 2.8V or 3.3V. So you could have ECSPI1 on 3.3V, ECSPI2 on 1.8V and ECSPI3 on 2.8V, for example. There's other signals, GPIOs etc. belonging to these power groups, so keep that in mind, as all I/Os within one power group will work on same operating voltage.
From IOMUX tool:
You can see that when using pin muxing options above, ECSPI1 signals belong to NVCC_EIM0 power group, ECSPI2 signals to NVCC_EIM1 and ECSPI3 to NVCC_LCD. Datasheet specifies voltage range for these power groups, which for EIM0, EIM1 and LCD are from 1.65V up to 3.6V, with typical values of 1.8V, 2.8V or 3.3V. So you could have ECSPI1 on 3.3V, ECSPI2 on 1.8V and ECSPI3 on 2.8V, for example. There's other signals, GPIOs etc. belonging to these power groups, so keep that in mind, as all I/Os within one power group will work on same operating voltage.
