Use the correct input type.

lib/python/qmk/xap/gen_firmware/header_generator.py

@@ -107,7 +107,7 @@ def generate_header(output_file, keyboard):
     lines.append(f'#define XAP_BCD_VERSION 0x{int(b.group(1)):02d}{int(b.group(2)):02d}{int(b.group(3)):04d}ul')
     b = prog.match(get_git_version())
     lines.append(f'#define QMK_BCD_VERSION 0x{int(b.group(1)):02d}{int(b.group(2)):02d}{int(b.group(3)):04d}ul')
-    keyboard_id = fnv1a_32(keyboard)
+    keyboard_id = fnv1a_32(bytes(keyboard, 'utf-8'))
     lines.append(f'#define XAP_KEYBOARD_IDENTIFIER 0x{keyboard_id:08X}ul')
     lines.append('')