bpf: Export cnum_umin/umax() helpers for netronome driver

bpf: Export cnum_umin/umax() helpers for netronome driver

ERROR: modpost: "cnum64_umin" [drivers/net/ethernet/netronome/nfp/nfp.ko] undefined!
ERROR: modpost: "cnum64_umax" [drivers/net/ethernet/netronome/nfp/nfp.ko] undefined!

Export symbols for these references.

Reported-by: Kaitao Cheng <pilgrimtao@gmail.com>
Fixes: bbc631085503 ("bpf: replace min/max fields with struct cnum{32,64}")
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260427112205.1346733-1-alan.maguire@oracle.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>