mlxsw: spectrum_trap: fix unintention integer overflow on left shift

Shifting the integer value 1 is evaluated using 32-bit
arithmetic and then used in an expression that expects a 64-bit
value, so there is potentially an integer overflow. Fix this
by using the BIT_ULL macro to perform the shift and avoid the
overflow.

Addresses-Coverity: ("Unintentional integer overflow")
Fixes: 13f2e64b ("mlxsw: spectrum_trap: Add devlink-trap policer support")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Tested-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>