dma-debug: fix return value of __setup handlers

When valid kernel command line parameters
  dma_debug=off dma_debug_entries=100
are used, they are reported as Unknown parameters and added to init's
environment strings, polluting it.

  Unknown kernel command line parameters "BOOT_IMAGE=/boot/bzImage-517rc5
    dma_debug=off dma_debug_entries=100", will be passed to user space.

and

 Run /sbin/init as init process
   with arguments:
     /sbin/init
   with environment:
     HOME=/
     TERM=linux
     BOOT_IMAGE=/boot/bzImage-517rc5
     dma_debug=off
     dma_debug_entries=100

Return 1 from these __setup handlers to indicate that the command line
option has been handled.

Fixes: 59d3daa ("dma-debug: add kernel command line parameters")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: Igor Zhbanov <i.zhbanov@omprussia.ru>
Link: lore.kernel.org/r/64644a2f-4a20-bab3-1e15-3b2cdd0defe3@omprussia.ru
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: iommu@lists.linux-foundation.org
Cc: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

kernel/dma/debug.c

@@ -927,7 +927,7 @@ static __init int dma_debug_cmdline(char *str)
 		global_disable = true;
 	}
 
-	return 0;
+	return 1;
 }
 
 static __init int dma_debug_entries_cmdline(char *str)
@@ -936,7 +936,7 @@ static __init int dma_debug_entries_cmdline(char *str)
 		return -EINVAL;
 	if (!get_option(&str, &nr_prealloc_entries))
 		nr_prealloc_entries = PREALLOC_DMA_DEBUG_ENTRIES;
-	return 0;
+	return 1;
 }
 
 __setup("dma_debug=", dma_debug_cmdline);