Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32f1/STM32F101/OTG_FS_GLOBAL/FS_GRXFSIZ#0x0
OTG_FS Receive FIFO size register (OTG_FS_GRXFSIZ)
RxFIFO depth
https://github.com/modm-io/cmsis-svd-stm32