[media] saa7164: measure via histograms various irq and queue latencies

saa7164: measure via histograms various irq and queue latencies
Attempting to determine where buffering issues under high load are due
to highly latent irq or work queue handling.

Signed-off-by: Steven Toth <stoth@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>