Typo in MSBFIRST usage in SparkFunLSM6DS3.cpp

[sbanzaert]

I think there is a mismatch between a defined constant used in SparkFunLSM6DS3.cpp vs what's defined in Arduino.h in the AVR core. This leads to an error when trying to compile, for example, MinimalistExample for the Uno:

In member function 'status_t LSM6DS3Core::beginCore()':
error: 'MSB_FIRST' was not declared in this scope
     mySpiSettings = SPISettings(spiPortSpeed, MSB_FIRST, SPI_MODE1);

The relevant line in SparkFunLSM6DS3.cpp is here
(which uses the constant MSB_FIRST to set up SPI)

However I believe this is meant to use a definition from Arduino.h in the AVR core, which is defined here as MSBFIRST (no underscore)