Library too large for smaller boards

```python
Adafruit CircuitPython 6.0.0-rc.1 on 2020-11-03; Adafruit QT Py M0 with samd21e18
>>> import adafruit_bno055
Traceback (most recent call last):
File "", line 1, in
File "adafruit_bno055.py", line 111, in
MemoryError: memory allocation failed, allocating 776 bytes
>>>
```

Reproduce the import failure on the Adafruit QT Py M0 with SAMD21E18 using CircuitPython 6.0.0-rc.1. Inspect adafruit_bno055.py, especially around line 111, and measure the library's memory use; the issue does not specify the intended reduction or a test, so the acceptable fix needs clarification.

Written by the indexing model from the issue text.