firmware-utils: add GPL 2.0 SPDX to files with no license info

These files fall under the project license: GPL-2.0-only.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>

tools/firmware-utils/src/bcm_tag.h

+// SPDX-License-Identifier: GPL-2.0-only
 #ifndef __BCM63XX_TAG_H
 #define __BCM63XX_TAG_H
 

tools/firmware-utils/src/bcmalgo.c

+// SPDX-License-Identifier: GPL-2.0-only
 #include <stdlib.h>
 #include <sys/types.h>
 #include <stdio.h>

tools/firmware-utils/src/bcmalgo.h

+// SPDX-License-Identifier: GPL-2.0-only
 #ifndef bcmutils_H
 #define bcmutils_H
 

tools/firmware-utils/src/dgfirmware.c

+// SPDX-License-Identifier: GPL-2.0-only
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>

tools/firmware-utils/src/hcsmakeimage.c

+// SPDX-License-Identifier: GPL-2.0-only
 #include <stdlib.h>
 #include <sys/types.h>
 #include <stdio.h>

tools/firmware-utils/src/mkdapimg.c

+// SPDX-License-Identifier: GPL-2.0-only
 #include <stdio.h>
 #include <stdint.h>
 #include <stdlib.h>

tools/firmware-utils/src/mksercommfw.c

+// SPDX-License-Identifier: GPL-2.0-only
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>

tools/firmware-utils/src/mktitanimg.c

+// SPDX-License-Identifier: GPL-2.0-only
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>

tools/firmware-utils/src/mktitanimg.h

+// SPDX-License-Identifier: GPL-2.0-only
 #ifndef __MKTITANIMG_H
 #define __MKTITANIMG_H
 

tools/firmware-utils/src/srec2bin.c

+// SPDX-License-Identifier: GPL-2.0-only
 #include <stdio.h>
 #include <ctype.h>
 #include <string.h>

tools/firmware-utils/src/trx2edips.c

+// SPDX-License-Identifier: GPL-2.0-only
 #include <stdio.h>
 #include <stdlib.h>
 #include <stddef.h>

tools/firmware-utils/src/utils.h

+// SPDX-License-Identifier: GPL-2.0-only
 #include <stdint.h>
 #include <string.h>
 

tools/firmware-utils/src/wrt400n.c

+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * WRT400n - Firmware Generation Creator
  *