You are not using the right SPI interface.
On mangOH Red, you have two SPI interfaces:
- One on IOT0 connector (SPI1).
- One on RPI connector (SPI2).
SPI2 on RPI connector of mangOH is connected to embedded WiFi/BT chipset (MT7697) via USB-to-SPI adapter (CP2130).
MT7697 is using CS0 chipselect from CP2130, but other chipselect signals (CS1 and CS2) are theoretically available to connect other slave devices.
As CP2130 driver is not pre-integrated into Linux system then I would encourage you to use the native SPI1 interface of WP7702 module which is available on IOT0 connector.