Giving a name to this enum makes it discoverable from
debugging tools like DRGN and SDB. For example, with
the name proposed on this patch we can iterate over
these values in DRGN:
```
>>> prog.type('enum kmc_bit').enumerators
(('KMC_BIT_NOTOUCH', 0), ('KMC_BIT_NODEBUG', 1),
('KMC_BIT_NOMAGAZINE', 2), ('KMC_BIT_NOHASH', 3),
('KMC_BIT_QCACHE', 4), ('KMC_BIT_KMEM', 5),
('KMC_BIT_VMEM', 6), ('KMC_BIT_SLAB', 7),
...
```
This enables SDB to easily pretty-print the flags of
the spl_kmem_caches in the system like this:
```
> spl_kmem_caches -o "name,flags,total_memory"
name flags total_memory
------------------------ ----------------------- ------------
abd_t KMC_NOMAGAZINE|KMC_SLAB 4.5MB
arc_buf_hdr_t_full KMC_NOMAGAZINE|KMC_SLAB 12.3MB
... <cropped> ...
ddt_cache KMC_VMEM 583.7KB
ddt_entry_cache KMC_NOMAGAZINE|KMC_SLAB 0.0B
... <cropped> ...
zio_buf_1048576 KMC_NODEBUG|KMC_VMEM 0.0B
... <cropped> ...
```
Reviewed-by: Matt Ahrens <matt@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Serapheim Dimitropoulos <serapheim@delphix.com>
Closes#9478
c19a6512fd