drm/msm: Fix missing include files in msm_gem.c

Include linux/vmalloc.h to fix below errors:
error: implicit declaration of function 'vmap'
Signed-off-by: Yanteng Si <siyanteng@loongson.cn>
Link: https://lore.kernel.org/r/15f30165e94574e4cd7c4da9f9c6fd1e320d4d8e.1634200323.git.siyanteng@loongson.cnSigned-off-by: Rob Clark <robdclark@chromium.org>

drivers/gpu/drm/msm/msm_gem.c

@@ -5,6 +5,7 @@
  */
 
 #include <linux/dma-map-ops.h>
+#include <linux/vmalloc.h>
 #include <linux/spinlock.h>
 #include <linux/shmem_fs.h>
 #include <linux/dma-buf.h>