[lld][ELF] Differentiate between Note sections(RW/RO)

It looks like there is a possibility of seeing RO/RW note sections
and we would need to create an appropriate RO/RW segment associated
with them.

Adds a test too.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@189907 91177308-0d34-0410-b5e6-96231b3b80d8
[lld][ELF] Change the order of the writable note section

Writable note sections if they exist should not appear before text
they belong in the data segment

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@190024 91177308-0d34-0410-b5e6-96231b3b80d8
[lld][cleanup] remove unused ReaderFunc to avoid confusion.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@190031 91177308-0d34-0410-b5e6-96231b3b80d8
Remove unused identifiers.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@190095 91177308-0d34-0410-b5e6-96231b3b80d8