use crypto/sha256 only for FIPS 140-2 compliance (#14983)

It would seem like the PR #11623 had chewed more
than it wanted to, non-fips build shouldn't really
be forced to use slower crypto/sha256 even for
presumed "non-performance" codepaths. In MinIO
there are really no "non-performance" codepaths.
This assumption seems to have had an adverse
effect in certain areas of CPU usage.

This PR ensures that we stick to sha256-simd
on all non-FIPS builds, our most common build
to ensure we get the best out of the CPU at
any given point in time.

internal/event/target/kafka_scram_client_contrib.go

@@ -17,11 +17,12 @@
 package target
 
 import (
-	"crypto/sha256"
 	"crypto/sha512"
 
 	"github.com/Shopify/sarama"
 	"github.com/xdg/scram"
+
+	"github.com/minio/minio/internal/hash/sha256"
 )
 
 func initScramClient(args KafkaArgs, config *sarama.Config) {