cbfstool: move iself() to eflheaders.c

The only user of iself() was in elfheaders.c. Move it there,
and make it local to the compilation unit.

Change-Id: I0d919ce372f6e2fce75885fb4fcba20d985979b3
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/5369
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: Marc Jones <marc.jones@se-eng.com>

util/cbfstool/common.c

@@ -23,7 +23,6 @@
 #include <stdlib.h>
 #include <string.h>
 #include <libgen.h>
-#include "elf.h"
 #include "common.h"
 #include "cbfs.h"
 
@@ -137,12 +136,6 @@ uint32_t string_to_arch(const char *arch_string)
 	return ret;
 }
 
-int iself(unsigned char *input)
-{
-	Elf32_Ehdr *ehdr = (Elf32_Ehdr *) input;
-	return !memcmp(ehdr->e_ident, ELFMAG, 4);
-}
-
 static struct filetypes_t {
 	uint32_t type;
 	const char *name;