candump: fix off-by-one error in dropcount calculation
candump: fix off-by-one error in dropcount calculation

Calculations using unsigned integer types are done modulo U*INT_MAX+1,
so you get the correct difference of two values by simply subtracting.
No special handling for overflow is neccessary.

Signed-off-by: Urs Thuermann <289c4a2cce68d99fb847fa5a2d1f81aecc99fcbc@isnogud.escape.de>
Signed-off-by: Oliver Hartkopp <06a38fb2ed1a2d0a17f4f06761ac2e5ace5a31ab@hartkopp.net>

carloop/can-utils-osx,carloop/can-utils-osx