Bluetooth: Move PRNG initialization a bit later in HCI init

Move the PRNG initialization after reading local supported commands,
so that we don't send HCI_LE_Rand if the controller doesn't support it
(we still need to fail the init however). The patch also removes a few
unnecessary #ifdefs related to crypto.h.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>