BQLmon: fix queue display with small terminals

The x_end - x_start comparison would be false too early, make sure we
use vq_end as the upper limit since it is correctly bounded.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
BQLmon: update README.md with a snapshot image

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>