modbus: fix quantity and count calculation

The [Modbus Spec S6.11](https://modbus.org/docs/Modbus_Application_Protocol_V1_1b.pdf)
clearly states that the `count = quantity / 8` and not the other way
around. This is fixed in sawp-0.5.0.

rust/Cargo.toml.in

@@ -33,8 +33,8 @@ widestring = "~0.4.3"
 flate2 = "~1.0.19"
 brotli = "~3.3.0"
 
-sawp-modbus = "~0.4.0"
-sawp = "~0.4.0"
+sawp-modbus = "~0.5.0"
+sawp = "~0.5.0"
 der-parser = "~4.0.2"
 kerberos-parser = "~0.5.0"
 ntp-parser = "~0.4.0"