atm: he: use 64-bit arithmetic instead of 32-bit

Add suffix ULL to constants 272, 204, 136 and 68 in order to give the
compiler complete information about the proper arithmetic to use.
Notice that these constants are used in contexts that expect
expressions of type unsigned long long (64 bits, unsigned).

The following expressions are currently being evaluated using 32-bit
arithmetic:

272 * mult
204 * mult
136 * mult
68 * mult

Addresses-Coverity-ID: 201058
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>