boot-wrapper-aarch64: use SPDX identifier for 3 clause BSD

Use the correct SPDX identifier for the 3 clause BSD license, like we do
elsewhere.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit f2d748e13be6ca119271af8487adda5856d43da4)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

boot/boot-wrapper-aarch64/boot-wrapper-aarch64.mk

@@ -6,7 +6,7 @@
 
 BOOT_WRAPPER_AARCH64_VERSION = 4266507a84f8c06452109d38e0350d4759740694
 BOOT_WRAPPER_AARCH64_SITE = git://git.kernel.org/pub/scm/linux/kernel/git/mark/boot-wrapper-aarch64.git
-BOOT_WRAPPER_AARCH64_LICENSE = BSD3c
+BOOT_WRAPPER_AARCH64_LICENSE = BSD-3-Clause
 BOOT_WRAPPER_AARCH64_LICENSE_FILES = LICENSE.txt
 BOOT_WRAPPER_AARCH64_DEPENDENCIES = linux
 BOOT_WRAPPER_AARCH64_INSTALL_IMAGES = YES