mm: Fix the flipped condition in gfpflags_allow_spinning()

The function gfpflags_allow_spinning() has a bug that makes it return
the opposite result than intended. This could contribute to deadlocks as
usage profilerates, for now it was noticed as a performance regression
due to try_charge_memcg() not refilling memcg stock when it could. Fix
the flipped condition.

Fixes: 97769a53 ("mm, bpf: Introduce try_alloc_pages() for opportunistic page allocation")
Reported-by: kernel test robot <oliver.sang@intel.com>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20250310124017.187-1-alexei.starovoitov@gmail.com
Closes: https://lore.kernel.org/oe-lkp/202503101254.cfd454df-lkp@intel.com


Signed-off-by: Alexei Starovoitov <ast@kernel.org>