icicle: protect ProvingKey.deviceInfo with mutex to prevent race condition

Concurrent calls to Prove() could simultaneously initialize pk.deviceInfo,
causing double initialization and GPU memory corruption.

Add setupMu sync.Mutex to ProvingKey struct and protect the entire
setupDevicePointers() function with Lock/Unlock. This ensures atomic
check-and-initialize semantics.

Author: p4u

backend/accelerated/icicle/groth16/bls12-377/icicle.go

@@ -64,6 +64,9 @@ func init() {
 }
 
 func (pk *ProvingKey) setupDevicePointers(device *icicle_runtime.Device) error {
+	pk.setupMu.Lock()
+	defer pk.setupMu.Unlock()
+	
 	if pk.deviceInfo != nil {
 		return nil
 	}

backend/accelerated/icicle/groth16/bls12-377/provingkey.go

@@ -1,6 +1,8 @@
 //go:build icicle
 
 import (
+	"sync"
+
 	"github.com/consensys/gnark-crypto/ecc/{{ toLower .Curve }}/fr"
 	groth16_{{ .CurvePkg }} "github.com/consensys/gnark/backend/groth16/{{ toLower .Curve }}"
 	icicle_core "github.com/ingonyama-zk/icicle-gnark/v3/wrappers/golang/core"
@@ -25,4 +27,5 @@ type deviceInfo struct {
 type ProvingKey struct {
 	groth16_{{ .CurvePkg }}.ProvingKey
 	*deviceInfo
+	setupMu sync.Mutex // Protects concurrent deviceInfo initialization
 }