Bluetooth: include scatterlist.h where needed

net/bluetooth/smp.c: In function 'smp_e':
net/bluetooth/smp.c:49:21: error: storage size of 'sg' isn't known
net/bluetooth/smp.c:67:2: error: implicit declaration of function 'sg_init_one'
net/bluetooth/smp.c:49:21: warning: unused variable 'sg'

Caused by commit d22ef0bc

 ("Bluetooth: Add LE SMP Cryptoolbox
functions").  Missing include file, presumably.  This batch has been in
the bluetooth tree since June 14, so it may have been exposed by the
removal of linux/mm.h from netdevice.h ...

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: John W. Linville <linville@tuxdriver.com>