dmaengine: pl330: rename _start to prevent build error

"_start" is used in several arches and proably should be reserved
for ARCH usage. Using it in a driver for a private symbol can cause
a build error when it conflicts with ARCH usage of the same symbol.

Therefore rename pl330's "_start" to "pl330_start_thread" so that there
is no conflict and no build error.

drivers/dma/pl330.c:1053:13: error: '_start' redeclared as different kind of symbol
 1053 | static bool _start(struct pl330_thread *thrd)
      |             ^~~~~~
In file included from ../include/linux/interrupt.h:21,
                 from ../drivers/dma/pl330.c:18:
arch/riscv/include/asm/sections.h:11:13: note: previous declaration of '_start' with type 'char[]'
   11 | extern char _start[];
      |             ^~~~~~

Fixes: b7d861d9 ("DMA: PL330: Merge PL330 driver into drivers/dma/")
Fixes: ae43b328 ("ARM: 8202/1: dmaengine: pl330: Add runtime Power Management support v12")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Jaswinder Singh <jassisinghbrar@gmail.com>
Cc: Boojin Kim <boojin.kim@samsung.com>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Vinod Koul <vkoul@kernel.org>
Cc: dmaengine@vger.kernel.org
Cc: linux-riscv@lists.infradead.org
Link: https://lore.kernel.org/r/20230524045310.27923-1-rdunlap@infradead.orgSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/pl330.c

@@ -1050,7 +1050,7 @@ static bool _trigger(struct pl330_thread *thrd)
 	return true;
 }
 
-static bool _start(struct pl330_thread *thrd)
+static bool pl330_start_thread(struct pl330_thread *thrd)
 {
 	switch (_state(thrd)) {
 	case PL330_STATE_FAULT_COMPLETING:
@@ -1702,7 +1702,7 @@ static int pl330_update(struct pl330_dmac *pl330)
 			thrd->req_running = -1;
 
 			/* Get going again ASAP */
-			_start(thrd);
+			pl330_start_thread(thrd);
 
 			/* For now, just make a list of callbacks to be done */
 			list_add_tail(&descdone->rqd, &pl330->req_done);
@@ -2089,7 +2089,7 @@ static void pl330_tasklet(struct tasklet_struct *t)
 	} else {
 		/* Make sure the PL330 Channel thread is active */
 		spin_lock(&pch->thread->dmac->lock);
-		_start(pch->thread);
+		pl330_start_thread(pch->thread);
 		spin_unlock(&pch->thread->dmac->lock);
 	}
 
@@ -2107,7 +2107,7 @@ static void pl330_tasklet(struct tasklet_struct *t)
 			if (power_down) {
 				pch->active = true;
 				spin_lock(&pch->thread->dmac->lock);
-				_start(pch->thread);
+				pl330_start_thread(pch->thread);
 				spin_unlock(&pch->thread->dmac->lock);
 				power_down = false;
 			}