[llvm-readelf] - --elf-hash-histogram: do not crash when the .gnu.hash goes past the EOF.

llvm-readelf might crash when the .gnu.hash table goes past the EOF.

This patch splits and updates the code of a helper function `checkGNUHashTable`,
which is similar to `checkHashTable` and fixes the issue.

Differential revision: https://reviews.llvm.org/D80215