net: hwbm: if CONFIG_NET_HWBM unset, make stub functions static

If CONFIG_NET_HWBM is not set, then these stub functions in
<net/hwbm.h> should be declared static to avoid trying to
export them from any driver that includes this.

Fixes the following sparse warnings:

./include/net/hwbm.h:24:6: warning: symbol 'hwbm_buf_free' was not declared. Should it be static?
./include/net/hwbm.h:25:5: warning: symbol 'hwbm_pool_refill' was not declared. Should it be static?
./include/net/hwbm.h:26:5: warning: symbol 'hwbm_pool_add' was not declared. Should it be static?

Signed-off-by: Ben Dooks (Codethink) <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/hwbm.h

···
 int hwbm_pool_refill(struct hwbm_pool *bm_pool, gfp_t gfp);
 int hwbm_pool_add(struct hwbm_pool *bm_pool, unsigned int buf_num);
 #else
-void hwbm_buf_free(struct hwbm_pool *bm_pool, void *buf) {}
-int hwbm_pool_refill(struct hwbm_pool *bm_pool, gfp_t gfp) { return 0; }
-int hwbm_pool_add(struct hwbm_pool *bm_pool, unsigned int buf_num)
+static inline void hwbm_buf_free(struct hwbm_pool *bm_pool, void *buf) {}
+
+static inline int hwbm_pool_refill(struct hwbm_pool *bm_pool, gfp_t gfp)
+{ return 0; }
+
+static inline int hwbm_pool_add(struct hwbm_pool *bm_pool,
+				unsigned int buf_num)
 { return 0; }
 #endif /* CONFIG_HWBM */
 #endif /* _HWBM_H */