hwtracing: stm: fix build error on some arches

commit 806e30873f0e74d9d41b0ef761bd4d3e55c7d510 upstream.

Commit b5e2ced9bf81 ("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: b5e2ced9bf81 ("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>

diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c
index b956305..c386451 100644
--- a/drivers/hwtracing/stm/core.c
+++ b/drivers/hwtracing/stm/core.c
@@ -27,6 +27,7 @@
 #include <linux/stm.h>
 #include <linux/fs.h>
 #include <linux/mm.h>
+#include <linux/vmalloc.h>
 #include "stm.h"
 
 #include <uapi/linux/stm.h>