small_SUITE: Improve test of mul/add combination #4629

Job	Run time
Event File	2s
Build Erlang/OTP (64-bit)	8m 20s
Create SBOM	0s
Build Erlang/OTP (iOS)	4m 7s
Build Erlang/OTP (32-bit)	5m 34s
Build Erlang/OTP (macOS)	2m 51s
Build Erlang/OTP (cross-compile)	10m 55s
Build Erlang/OTP (Types and Flavors)	10m 39s
Build Erlang/OTP (clang)	5m 42s
Build Erlang/OTP (Windows)	18m 28s
Build and check documentation	4m 55s
Build Erlang/OTP (FreeBSD)	3m 27s
Run static analysis	6m 3s
Test Erlang/OTP (emulator)	49m 19s
Test Erlang/OTP (debug)	4m 33s
Test Erlang/OTP (stdlib)	1h 7m 52s
Test Erlang/OTP (tools)	4m 39s
Release Erlang/OTP	0s
Test Erlang/OTP (system)	7m 15s
	3h 34m 41s

Provide feedback