net/fungible: CONFIG_FUN_CORE needs SBITMAP

fun_core.ko uses sbitmaps and needs to select SBITMAP.
Fixes below errors:

ERROR: modpost: "__sbitmap_queue_get"
[drivers/net/ethernet/fungible/funcore/funcore.ko] undefined!
ERROR: modpost: "sbitmap_finish_wait"
[drivers/net/ethernet/fungible/funcore/funcore.ko] undefined!
ERROR: modpost: "sbitmap_queue_clear"
[drivers/net/ethernet/fungible/funcore/funcore.ko] undefined!
ERROR: modpost: "sbitmap_prepare_to_wait"
[drivers/net/ethernet/fungible/funcore/funcore.ko] undefined!
ERROR: modpost: "sbitmap_queue_init_node"
[drivers/net/ethernet/fungible/funcore/funcore.ko] undefined!
ERROR: modpost: "sbitmap_queue_wake_all"
[drivers/net/ethernet/fungible/funcore/funcore.ko] undefined!

v2: correct "Fixes" SHA

Fixes: 749efb1e ("net/fungible: Kconfig, Makefiles, and MAINTAINERS")
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Dimitris Michailidis <dmichail@fungible.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: David S. Miller <davem@davemloft.net>