mm/zonelist: enumerate zonelists array index

Hardcoding index to zonelists array in gfp_zonelist() is not a good
idea, let's enumerate it to improve readability.

No functional change.

[[email protected]: coding-style fixes]
[[email protected]: fix CONFIG_NUMA=n build]
[[email protected]: fix warning in comparing enumerator]
Signed-off-by: Yaowei Bai <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: David Rientjes <[email protected]>
Signed-off-by: Naoya Horiguchi <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
3 files changed