page_pool: fix compile warning when CONFIG_PAGE_POOL is disabled

Kbuild test robot reported compile warning:
warning: no return statement in function returning non-void
in function page_pool_request_shutdown, when CONFIG_PAGE_POOL is disabled.

The fix makes the code a little more verbose, with a descriptive variable.

Fixes: 99c07c43c4ea ("xdp: tracking page_pool resources and safe removal")
Signed-off-by: Jesper Dangaard Brouer <[e-mail]>
Reported-by: kbuild test robot <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/page_pool.h

···
 bool __page_pool_request_shutdown(struct page_pool *pool);
 static inline bool page_pool_request_shutdown(struct page_pool *pool)
 {
-	/* When page_pool isn't compiled-in, net/core/xdp.c doesn't
-	 * allow registering MEM_TYPE_PAGE_POOL, but shield linker.
-	 */
+	bool safe_to_remove = false;
+
 #ifdef CONFIG_PAGE_POOL
-	return __page_pool_request_shutdown(pool);
+	safe_to_remove = __page_pool_request_shutdown(pool);
 #endif
+	return safe_to_remove;
 }
 
 /* Disconnects a page (from a page_pool).  API users can have a need