util/cbfstool: Print all supported architectures

The list of supported architectures in the usage output of cbfstool is
currently hardcoded and outdated.

Use the arch_names array in common.c to provide and up-to-date list.

Change-Id: I3e7ed67c3bfd928b304c314fcc8e1bea35561662
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-on: https://review.coreboot.org/25590
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

util/cbfstool/common.h

@@ -204,6 +204,7 @@ int parse_elf_to_stage(const struct buffer *input, struct buffer *output,
 int parse_elf_to_xip_stage(const struct buffer *input, struct buffer *output,
 				uint32_t *location, const char *ignore_section);
 
+void print_supported_architectures(void);
 void print_supported_filetypes(void);
 
 /* lzma/lzma.c */