ANDROID: trusty: use flexible arrays instead of zero-length arrays

Follow the recommended kernel coding style.
See https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays



Test: trusty/vendor/google/aosp/scripts/build.py qemu-generic-arm64-test-debug
Change-Id: I435731f8148a9efad57dbe70327f8395ab9c99c4
Signed-off-by: Eric Biggers <ebiggers@google.com>