hexiwear_k64: Add sensor dts nodes and fixups

Adds dts nodes and fixups for the fxos8700, fxas21002, and max30101
sensors to the hexiwear_k64 board. Tested with:
- samples/sensor/fxos8700
- samples/sensor/fxas21002
- samples/sensor/max30101

Signed-off-by: Maureen Helm <maureen.helm@nxp.com>