libebl: Fix missing brackets around if statement body.

libebl: Fix missing brackets around if statement body.

GCC6 [will have] a nice new warning that showed a real bug:

elfutils/libebl/eblobjnote.c: In function ‘ebl_object_note’:
elfutils/libebl/eblobjnote.c:135:5: error: statement is indented as if it were guarded by... [-Werror=misleading-indentation]
     switch (type)
     ^~~~~~

elfutils/libebl/eblobjnote.c:45:3: note: ...this ‘if’ clause, but it is not
   if (! ebl->object_note (name, type, descsz, desc))
   ^~

And indeed, it should have been under the if, but wasn't because of missing
brackets. Added brackets (and reindent).

Signed-off-by: Mark Wielaard <mjw@redhat.com>