west: sign.py: fix logic bug

Fix bug where if `CONFIG_BOOTLOADER_MCUBOOT` is set sign.py incorrectly
shows warning `CONFIG_BOOTLOADER_MCUBOOT is not set to y...`.

Signed-off-by: Arvin Farahmand <arvinf@ip-logix.com>

scripts/west_commands/sign.py

@@ -220,7 +220,7 @@ def sign(self, command, build_dir, build_conf, formats):
         flash = self.edt_flash_node(b, args.quiet)
         align, addr, size = self.edt_flash_params(flash)
 
-        if build_conf.getboolean('CONFIG_BOOTLOADER_MCUBOOT'):
+        if not build_conf.getboolean('CONFIG_BOOTLOADER_MCUBOOT'):
             log.wrn("CONFIG_BOOTLOADER_MCUBOOT is not set to y in "
                     f"{build_conf.path}; this probably won't work")