[ELF] Make --fix-cortex-a53-843419 work on big endian hosts

The reinterpret cast to uint32_t to read the little-endian instructions 
will only work on a little endian system. Use ulittle32_t to always read
little-endian (AArch64 instructions are always little endian).

Fixes PR36056

Differential Revision: https://reviews.llvm.org/D42421

llvm-svn: 323243