The CCM specification (NIST SP 800-38C) mandates that the formatting of
the additional data length l(a) changes when it is greater _or equal_ to
2^16 - 2^8 (>= 0xFF00). Since such lengths are not supported in mbed TLS,
the operation should fail in such cases.
This commit fixes an off-by-one error which allowed encryption/decryption
to be executed when l(a) was equal to 0xFF00, resulting in an
incorrect/non-standard length format being used.
Fixes#3719.
Signed-off-by: Fredrik Strupe <fredrik.strupe@silabs.com>
