Fix sizeof-pointer-memaccess warning with gcc 4.8

This patch fixes wrong memcpy size when copying ltk value to
HCI_OP_LE_LTK_REPLY command.

Change-Id: I44e5e3da15369d4b424581720ccd3bac820ef2e0
Linaro 4.8 bring-up
More GCC 4.8+ config fixes