[llvm-objcopy] Improve command line option help messages

I was being inconsistent with the way I was capitalizing help messages
for command line options. Additionally --remove-section wasn't using
value_desc even though it benefited from it.

Differential Revision: https://reviews.llvm.org/D39978

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@318190 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed