objtool: Fix memory leak in create_static_call_sections()

strdup() allocates memory for key_name. We need to release the memory in
the following error paths. Add free() to avoid memory leak.

Fixes: 1e7e4788 ("x86/static_call: Add inline static call implementation for x86-64")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20221205080642.558583-1-linmq006@gmail.com
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>