dmaengine: ti: k3-udma: Add missing locking

Recent kernels complain about a missing lock in k3-udma.c when the lock
validator is enabled:

[    4.128073] WARNING: CPU: 0 PID: 746 at drivers/dma/ti/../virt-dma.h:169 udma_start.isra.0+0x34/0x238
[    4.137352] CPU: 0 UID: 0 PID: 746 Comm: kworker/0:3 Not tainted 6.12.9-arm64 #28
[    4.144867] Hardware name: pp-v12 (DT)
[    4.148648] Workqueue: events udma_check_tx_completion
[    4.153841] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[    4.160834] pc : udma_start.isra.0+0x34/0x238
[    4.165227] lr : udma_start.isra.0+0x30/0x238
[    4.169618] sp : ffffffc083cabcf0
[    4.172963] x29: ffffffc083cabcf0 x28: 0000000000000000 x27: ffffff800001b005
[    4.180167] x26: ffffffc0812f0000 x25: 0000000000000000 x24: 0000000000000000
[    4.187370] x23: 0000000000000001 x22: 00000000e21eabe9 x21: ffffff8000fa0670
[    4.194571] x20: ffffff8001b6bf00 x19: ffffff8000fa0430 x18: ffffffc083b95030
[    4.201773] x17: 0000000000000000 x16: 00000000f0000000 x15: 0000000000000048
[    4.208976] x14: 0000000000000048 x13: 0000000000000000 x12: 0000000000000001
[    4.216179] x11: ffffffc08151a240 x10: 0000000000003ea1 x9 : ffffffc08046ab68
[    4.223381] x8 : ffffffc083cabac0 x7 : ffffffc081df3718 x6 : 0000000000029fc8
[    4.230583] x5 : ffffffc0817ee6d8 x4 : 0000000000000bc0 x3 : 0000000000000000
[    4.237784] x2 : 0000000000000000 x1 : 00000000001fffff x0 : 0000000000000000
[    4.244986] Call trace:
[    4.247463]  udma_start.isra.0+0x34/0x238
[    4.251509]  udma_check_tx_completion+0xd0/0xdc
[    4.256076]  process_one_work+0x244/0x3fc
[    4.260129]  process_scheduled_works+0x6c/0x74
[    4.264610]  worker_thread+0x150/0x1dc
[    4.268398]  kthread+0xd8/0xe8
[    4.271492]  ret_from_fork+0x10/0x20
[    4.275107] irq event stamp: 220
[    4.278363] hardirqs last  enabled at (219): [<ffffffc080a27c7c>] _raw_spin_unlock_irq+0x38/0x50
[    4.287183] hardirqs last disabled at (220): [<ffffffc080a1c154>] el1_dbg+0x24/0x50
[    4.294879] softirqs last  enabled at (182): [<ffffffc080037e68>] handle_softirqs+0x1c0/0x3cc
[    4.303437] softirqs last disabled at (177): [<ffffffc080010170>] __do_softirq+0x1c/0x28
[    4.311559] ---[ end trace 0000000000000000 ]---

This commit adds the missing locking.

Fixes: 25dcb5dd ("dmaengine: ti: New driver for K3 UDMA")
Cc: Peter Ujfalusi <peter.ujfalusi@gmail.com>
Cc: Vignesh Raghavendra <vigneshr@ti.com>
Cc: Vinod Koul <vkoul@kernel.org>
Cc: dmaengine@vger.kernel.org
Cc: stable@vger.kernel.org
Signed-off-by: Ronald Wahl <ronald.wahl@legrand.com>
Acked-by: Peter Ujfalusi <peter.ujfalusi@gmail.com>
Link: https://lore.kernel.org/r/20250414173113.80677-1-rwahl@gmx.de


Signed-off-by: Vinod Koul <vkoul@kernel.org>