scsi: bfa: document overflow of io_profile_start_time

io_profile_start_time() gets read using do_gettimeofday() and passed
down as a 32-bit value through multiple functions. This will overflow in
y2038 or y2106, depending on whether it gets interpreted as unsigned in
the end.

This changes do_gettimeofday() to ktime_get_real_seconds() and pushes
the point at which it overflows to where we actually assign it to the
bfa_fcpim_del_itn_stats_s structure, with an appropriate comment.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Anil Gurumurthy <Anil.Gurumurthy@cavium.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>