util: change coreboot to lowercase

The word 'coreboot' should always be written in lowercase, even at the
start of a sentence.

Change-Id: I0a024d82d331c0794fe087e440b4e1924129a13c
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/20030
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

util/cbfstool/cbfs-mkstage.c

@@ -313,7 +313,7 @@ int parse_elf_to_stage(const struct buffer *input, struct buffer *output,
 	outheader.data = output->data;
 	outheader.size = 0;
 
-	/* Coreboot expects entry point to be physical address. Thus, adjust the
+	/* coreboot expects entry point to be physical address. Thus, adjust the
 	 * entry point accordingly.
 	 */
 	fill_cbfs_stage(&outheader, algo, ehdr->e_entry + virt_to_phys,