MC: honour IMAGE_SCN_CNT_INITIALIZED_DATA

Emit the flag to indicate to the assembler that a section contains data if there
is pre-populated data present.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207028 91177308-0d34-0410-b5e6-96231b3b80d8
MC: move ARM64 test from AArch64 directory

The test was changed from aarch64 to arm64 but not moved.  The test would fail
if the backend was not built.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207029 91177308-0d34-0410-b5e6-96231b3b80d8