bnx2x: use ktime_get_seconds() for timestamp

commit c48f350f "bnx2x: Add MFW dump support" added the
bnx2x_update_mfw_dump() function that reads the current time and stores
it in a 32-bit field that gets passed into a buffer in a fixed format.

This is potentially broken when the epoch overflows in 2038, and
otherwise overflows in 2106. As we're trying to avoid uses of
struct timeval for this reason, I noticed the addition of this
function, and tried to rewrite it in a way that is more explicit
about the overflow and that will keep working once we deprecate
struct timeval.

I assume that it is not possible to change the ABI any more, otherwise
we should try to use a 64-bit field for the seconds right away.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Yuval Mintz <Yuval.Mintz@qlogic.com>
Cc: Ariel Elior <Ariel.Elior@qlogic.com>
Acked-by: Yuval Mintz <Yuval.Mintz@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>