You get the answer by reading the STE2007 controller datasheet thoroughly.
Incomplete data bytes are discarded by the controller. Means if you are using a hardware SPI interface, which can send multiples of 8 bit only, you have to send e.g. 2 bytes (16 bits) to transfer 9 bit of data, but 7 bits are discarded.
Alternatively, you can send the d/c bit by bit banging and send data/command bytes through the hardware interface, you save the bit shift required otherwise. But the method involves enabling and disabling of the SPI interface.