Is there any ethernet port? - console port! -
If not it is a SX6005 FDR switch that externally managed that doesn't include SM.
SX6012 is a FDR switch with SM.
Your dump shows a word LID...:)
I think you have a InfiniBand switch - not ethernet switch -
You said that you used flint that can flash firmware only - not boot image.
I think also clear boot bank on NAND then re-program include re-partition and upload each boot images.
Custom or any 3rd party image uploader can't support like Mellanox's done on their platform.
Unfortunately I don't have Seitch-X product yet...:(
But you will be recover boot bank on u-boot console by my experience...:)
Don't give it up!
Have a nice day...:)