[scudo] Improve readability of MemMapFuchsia's error handling (#90102)

By expressing the conditions covered by MAP_ALLOWNOMEM in a more
direct way.

GitOrigin-RevId: b7e9dae6f6a4610bee729179167a0ac4a3dd7b7b
Change-Id: I09a1adb12af85b08c6b5fb34051ed7d162998f00
1 file changed