mmap(2) should check whether return value is MAP_FAILED instead of NULL

[corona10]

According to the man page, mmap(2) returns MAP_FAILED (-1) on error instead of NULL. by @namhyung

Linked PRs

• gh-113343: Fix error check on mmap(2) #113342
• [3.12] gh-113343: Fix error check on mmap(2) (GH-113342) #113374