selftests/dma: fix invalid array access in printf

The printf statement attempts to print the DMA direction string using
the syntax 'dir[directions]', which is an invalid array access. The
variable 'dir' is an integer, and 'directions' is a char pointer array.
This incorrect syntax should be 'directions[dir]', using 'dir' as the
index into the 'directions' array. Fix this by correcting the array
access from 'dir[directions]' to 'directions[dir]'.

Link: https://lore.kernel.org/r/20251104025234.2363-1-zhangchujun@cmss.chinamobile.com
Signed-off-by: Zhang Chujun <zhangchujun@cmss.chinamobile.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Author: Zhang Chujun

tools/testing/selftests/dma/dma_map_benchmark.c

@@ -118,7 +118,7 @@ int main(int argc, char **argv)
 	}
 
 	printf("dma mapping benchmark: threads:%d seconds:%d node:%d dir:%s granule: %d\n",
-			threads, seconds, node, dir[directions], granule);
+			threads, seconds, node, directions[dir], granule);
 	printf("average map latency(us):%.1f standard deviation:%.1f\n",
 			map.avg_map_100ns/10.0, map.map_stddev/10.0);
 	printf("average unmap latency(us):%.1f standard deviation:%.1f\n",