tools/slabinfo-gnuplot: force to use bash shell

On some linux distributions, the default link of sh is dash which
deoesn't support split array like "${var//,/ }"

It's better to force to use bash shell directly.

Link: http://lkml.kernel.org/r/20171208093751.GA175471@sofia
Signed-off-by: Liu Changcheng <[email protected]>
Reviewed-by: Sergey Senozhatsky <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

tools/vm/slabinfo-gnuplot.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 
 # Sergey Senozhatsky, 2015
 # [email protected]