atm: mpoa: remove 32-bit timekeeping

net/atm/mpoa_* files use 'struct timeval' to store event
timestamps. struct timeval uses a 32-bit seconds field which will
overflow in the year 2038 and beyond. Morever, the timestamps are being
compared only to get seconds elapsed, so struct timeval which stores
a seconds and microseconds field is an overkill. This patch replaces
the use of struct timeval with time64_t to store a 64-bit seconds field.

Signed-off-by: Tina Ruchandani <ruchandani.tina@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>