kmsan: include linux/vmalloc.h

This is needed for the vmap/vunmap declarations:

mm/kmsan/kmsan_test.c:316:9: error: implicit declaration of function 'vmap' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
        vbuf = vmap(pages, npages, VM_MAP, PAGE_KERNEL);
               ^
mm/kmsan/kmsan_test.c:316:29: error: use of undeclared identifier 'VM_MAP'
        vbuf = vmap(pages, npages, VM_MAP, PAGE_KERNEL);
                                   ^
mm/kmsan/kmsan_test.c:322:3: error: implicit declaration of function 'vunmap' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
                vunmap(vbuf);
                ^

Link: https://lkml.kernel.org/r/20221215163046.4079767-1-arnd@kernel.org
Fixes: 8ed691b0 ("kmsan: add tests for KMSAN")
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Reviewed-by: NAlexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

mm/kmsan/kmsan_test.c

@@ -22,6 +22,7 @@
 #include <linux/spinlock.h>
 #include <linux/string.h>
 #include <linux/tracepoint.h>
+#include <linux/vmalloc.h>
 #include <trace/events/printk.h>
 
 static DEFINE_PER_CPU(int, per_cpu_var);