objtool: Use Elf_Scn typedef instead of assuming struct name

The libelf implementation might use a different struct name, and the
Elf_Scn typedef is already used throughout the rest of objtool.

Signed-off-by: Michael Forney <mforney@mforney.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/d270e1be2835fc2a10acf67535ff2ebd2145bf43.1562793448.git.jpoimboe@redhat.com

tools/objtool/elf.c

@@ -463,7 +463,7 @@ struct section *elf_create_section(struct elf *elf, const char *name,
 {
 	struct section *sec, *shstrtab;
 	size_t size = entsize * nr;
-	struct Elf_Scn *s;
+	Elf_Scn *s;
 	Elf_Data *data;
 
 	sec = malloc(sizeof(*sec));