contexthub-nano: Include headers for 4.4 kernels

* Still builds fine on 3.18 as well (not that we care).

* Relevant error snippet:
```
device/google/contexthub/contexthubhal/NanohubHidlAdapter.cpp
device/google/contexthub/contexthubhal/NanohubHidlAdapter.cpp:527:25: error: use of undeclared identifier 'O_RDONLY'
    int fd = open(file, O_RDONLY);
                        ^
1 error generated.
17:51:51 ninja failed with: exit status 1
```

Change-Id: I7ec26215feb5b0065987168222311f699472c466
2 files changed