Add a local logging function to emit bluetooth specific
messages.  Using vsprintf extension %pV saves code/text
space.

Convert the current BT_INFO and BT_ERR macros to use bt_printk.
Remove __func__ from BT_ERR macro (and the uses).
Prefix "Bluetooth: " to BT_ERR
Remove __func__ from BT_DBG as function can be prefixed when
using dynamic_debug.

With allyesconfig:

   text    data     bss     dec     hex filename
 129956    8632   36096  174684   2aa5c drivers/bluetooth/built-in.o.new2
 134402    8632   36064  179098   2bb9a drivers/bluetooth/built-in.o.old
  14778    1012    3408   19198    4afe net/bluetooth/bnep/built-in.o.new2
  15067    1012    3408   19487    4c1f net/bluetooth/bnep/built-in.o.old
 346595   19163   86080  451838   6e4fe net/bluetooth/built-in.o.new2
 353751   19163   86064  458978   700e2 net/bluetooth/built-in.o.old
  18483    1172    4264   23919    5d6f net/bluetooth/cmtp/built-in.o.new2
  18927    1172    4264   24363    5f2b net/bluetooth/cmtp/built-in.o.old
  19237    1172    5152   25561    63d9 net/bluetooth/hidp/built-in.o.new2
  19581    1172    5152   25905    6531 net/bluetooth/hidp/built-in.o.old
  59461    3884   14464   77809   12ff1 net/bluetooth/rfcomm/built-in.o.new2
  61206    3884   14464   79554   136c2 net/bluetooth/rfcomm/built-in.o.old

with x86 defconfig (and just bluetooth):

$ size net/bluetooth/built-in.o.defconfig.*
   text    data     bss     dec     hex filename
  66358     933     100   67391   1073f net/bluetooth/built-in.o.defconfig.new
  66643     933     100   67676   1085c net/bluetooth/built-in.o.defconfig.old

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>