Bluetooth: Remove `BT_HEXDUMP_DBG`

Replace unnecessary `BT_HEXDUMP_DBG` with `LOG_HEXDUMP_DBG`.

`BT_HEXDUMP_DBG` did an extra cast to `const uint8_t *` on its first
argument. This was probably the reason it was introduced. But the
current definition of `LOG_HEXDUMP_DBG` does this cast for us.

Signed-off-by: Théo Battrel <theo.battrel@nordicsemi.no>