In a typical setting where int is 32 bits and the type guint8 is 8 bits,
the overflow check in Dot11DecryptDerivePmkFromMsk will automatically
promote the sum of msk_len and *pmk_len to an int. Since int is 32 bits
and guint8 will always be 8 bits, the sum will never overflow.
Therefore, an explicit casting of the sum of msk_len and *pmk_len to
the type guint8 is necessary.
Signed-off-by: Elijah Conners <business@elijahpepe.com>