lib/generic-radix-tree.c: make 2 functions static inline

lib/generic-radix-tree.c: make 2 functions static inline

When building with W=1, we get some warnings:

l  CC      lib/generic-radix-tree.o
lib/generic-radix-tree.c:39:10: warning: no previous prototype for 'genradix_root_to_depth' [-Wmissing-prototypes]
   39 | unsigned genradix_root_to_depth(struct genradix_root *r)
      |          ^~~~~~~~~~~~~~~~~~~~~~
lib/generic-radix-tree.c:44:23: warning: no previous prototype for 'genradix_root_to_node' [-Wmissing-prototypes]
   44 | struct genradix_node *genradix_root_to_node(struct genradix_root *r)
      |                       ^~~~~~~~~~~~~~~~~~~~~

They're not used anywhere else, so make them static inline.

Link: http://lkml.kernel.org/r/46923.1565236485@turing-police
Signed-off-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>