mm: fix a typo in comment "strucure"->"structure"

There is a typo in comment, fix it.
Signed-off-by: Ethon Paul <ethp@qq.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
Link: http://lkml.kernel.org/r/20200411064723.15855-1-ethp@qq.comSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/internal.h

@@ -132,7 +132,7 @@ extern pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address);
  *
  * zonelist, preferred_zone and highest_zoneidx are set first in
  * __alloc_pages_nodemask() for the fast path, and might be later changed
- * in __alloc_pages_slowpath(). All other functions pass the whole strucure
+ * in __alloc_pages_slowpath(). All other functions pass the whole structure
  * by a const pointer.
  */
 struct alloc_context {