sock: Code cleanup on __sk_mem_raise_allocated()

Code cleanup for both better simplicity and readability.
No functional change intended.

Signed-off-by: Abel Wu <wuyun.abel@bytedance.com>
Acked-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20231019120026.42215-1-wuyun.abel@bytedance.com


Signed-off-by: Paolo Abeni <pabeni@redhat.com>