hwtracing: stm: fix build error on some arches

BugLink: https://bugs.launchpad.net/bugs/1776177

commit 806e3087 upstream.

Commit b5e2ced9 ("stm class: Use vmalloc for the master map") caused
a build error on some arches as vmalloc.h was not explicitly included.

Fix that by adding it to the list of includes.

Fixes: b5e2ced9 ("stm class: Use vmalloc for the master map")
Reported-by: kbuild test robot <lkp@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

drivers/hwtracing/stm/core.c

@@ -26,6 +26,7 @@
 #include <linux/stm.h>
 #include <linux/fs.h>
 #include <linux/mm.h>
+#include <linux/vmalloc.h>
 #include "stm.h"
 
 #include <uapi/linux/stm.h>