bluetooth: host: hci_core: fix `num_handles` assignment

Replaced `sys_cpu_to_le16(1)` with a direct `1` assignment to the
`cp->num_handles` (uint8_t) field to avoid truncation to `0x00` on
big-endian architectures.

Signed-off-by: Pisit Sawangvonganan <pisit@ndrsolution.com>