In SDK 9.2, the size of the R5 binary has increased and incase of USB DFU boot if binary size exceeds 512KB then it appears that the ROM is failing to load the tiboot3.bin. (No logs can be seen at all in console)

WA:
When tiboot3.bin size is reduced by removing some config options, ROM is able to load the execute the R5 SPL.

Remove CONFIG_SPL_FS_LOADER option from r5 defconfig to get USB DFU working