objtool: Add empty symbols to the symbol tree again

objtool: Add empty symbols to the symbol tree again

The following commit

  5da6aea375cd ("objtool: Fix find_{symbol,func}_containing()")

fixed the issue where overlapping symbols weren't getting sorted
properly in the symbol tree.  Therefore the workaround to skip adding
empty symbols from the following commit

  a2e38dffcd93 ("objtool: Don't add empty symbols to the rbtree")

is no longer needed.

Acked-by: Petr Mladek <pmladek@suse.com>
Tested-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>