mm: fix CONFIG_STACK_GROWSUP typo in mm.h

mm: fix CONFIG_STACK_GROWSUP typo in mm.h

Commit 2b6a3f061f11 ("mm: declare VMA flags by bit") significantly
refactors the header file include/linux/mm.h.  In that step, it introduces
a typo in an ifdef, referring to a non-existing config option
STACK_GROWS_UP, whereas the actual config option is called STACK_GROWSUP.

Fix this typo in the mm header file.

Link: https://lkml.kernel.org/r/20251201122922.352480-1-lukas.bulwahn@redhat.com
Fixes: 2b6a3f061f11 ("mm: declare VMA flags by bit")
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@redhat.com>
Acked-by: David Hildenbrand (Red Hat) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>