cbfstool: Eliminate global variable "arch"

Now that unused functions have been removed, the global "arch" is only
used in very few places. We can pack "arch" in the "param" structure
and pass it down to where it is actually used.

Change-Id: I255d1e2bc6b5ead91b6b4e94a0202523c4ab53dc
Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-on: http://review.coreboot.org/5105
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

util/cbfstool/cbfs.h

@@ -129,6 +129,7 @@ uint32_t get_cbfs_compression(const char *name, uint32_t unknown);
 /* elfheaders.c */
 int
 elf_headers(const struct buffer *pinput,
+	    uint32_t arch,
 	    Elf64_Ehdr *ehdr,
 	    Elf64_Phdr **pphdr,
 	    Elf64_Shdr **pshdr);