scsi:ufs Async suspend/resume callbacks.

The UFS callback is the most time consuming callback in the dpm_resume
section of kernel resumes, taking around 30 ms. Making it async
improves resume latency by around 20 ms, and helps with decreasing
suspend times as well.

Bug: 134704391
Change-Id: I708c8a7bc8f2250d6b2365971ccc394c7fbf8896
Signed-off-by: Vincent Palomares <paillon@google.com>

drivers/scsi/ufs/ufshcd.c

@@ -13185,6 +13185,8 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
 
 	ufshcd_add_sysfs_nodes(hba);
 
+	device_enable_async_suspend(dev);
+
 	return 0;
 
 out_remove_scsi_host: