Bluetooth: SMP_BR: Use macros instead of hard code

Define macros for encryption value,
#define BT_HCI_ENCRYPTION_OFF           0x00
#define BT_HCI_ENCRYPTION_ON_LE_AES_CCM 0x01
#define BT_HCI_ENCRYPTION_ON_BR_E0      0x01
#define BT_HCI_ENCRYPTION_ON_BR_AES_CCM 0x02

Use the macros to replace the hard code.

Signed-off-by: Lyle Zhu <lyle.zhu@nxp.com>