core/vm: optimize osakaMultComplexity

[cuiweixie]

func BenchmarkOsakaMultComplexity(b *testing.B) {
	var input uint64 = 123456789
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		_ = osakaMultComplexity(input)
	}
}

goos: darwin
goarch: arm64
pkg: github.com/ethereum/go-ethereum/core/vm
cpu: Apple M1 Pro
                       │   old.txt    │               new.txt               │
                       │    sec/op    │    sec/op     vs base               │
OsakaMultComplexity-10   0.3145n ± 1%   0.3124n ± 0%  -0.68% (p=0.003 n=10)

                       │  old.txt   │            new.txt             │
                       │    B/op    │    B/op     vs base            │
OsakaMultComplexity-10   0.000 ± 0%   0.000 ± 0%  ~ (p=1.000 n=10) ¹
¹ all samples are equal

                       │  old.txt   │            new.txt             │
                       │ allocs/op  │ allocs/op   vs base            │
OsakaMultComplexity-10   0.000 ± 0%   0.000 ± 0%  ~ (p=1.000 n=10) ¹
¹ all samples are equal

[rjl493456442]

OsakaMultComplexity-10 0.3145n ± 1% 0.3124n ± 0% -0.68% (p=0.003 n=10)

no difference?

[cuiweixie]

OsakaMultComplexity-10 0.3145n ± 1% 0.3124n ± 0% -0.68% (p=0.003 n=10)

no difference?
base on implementation, minor improvements.

[rjl493456442]

Since the performance difference is negligible, i would prefer to not include this change