Update transceive for repeated start for #8

[caternuson]

Possible fix for #8.

Tested on RPI with back to back runs after CTRL-C:

pi@raspberrypi:~$ python3 mlx90393_simpletest.py 
[9544.019423779]
X: -331.5 uT
Y: 30.299999999999997 uT
Z: 193.6 uT
[9545.033419421]
X: -332.25 uT
Y: 37.8 uT
Z: 189.728 uT
[9546.047318705]
X: -332.55 uT
Y: 18.15 uT
Z: 197.23 uT
[9547.061402465]
X: -330.0 uT
Y: 18.3 uT
Z: 197.956 uT
^CTraceback (most recent call last):
  File "mlx90393_simpletest.py", line 19, in <module>
    time.sleep(1.0)
KeyboardInterrupt
pi@raspberrypi:~$ python3 mlx90393_simpletest.py 
[9551.104622749]
X: -343.95 uT
Y: 29.849999999999998 uT
Z: 182.71 uT
[9552.118655711]
X: -334.8 uT
Y: 20.099999999999998 uT
Z: 196.262 uT
^CTraceback (most recent call last):
  File "mlx90393_simpletest.py", line 19, in <module>
    time.sleep(1.0)
KeyboardInterrupt

and on a Metro M4 to make sure nothing broke there:

Press any key to enter the REPL. Use CTRL-D to reload.
Adafruit CircuitPython 4.0.1 on 2019-05-22; Adafruit Metro M4 Express with samd51j19
>>> import mlx90393_simpletest
[96.266]
X: -301.2 uT
Y: 120.75 uT
Z: 139.876 uT
[97.279]
X: -314.7 uT
Y: 126.0 uT
Z: 144.716 uT

[jerryneedell]

tested on Raspberry Pi 3B+ -- repeated starts worked OK (3 times)
also tested on pyportal - no problems
Looks good to me!