The driver cannot compile with Mbed OS 5.11.2 and above.

[screamerbg]

Due to the following change ARMmbed/mbed-os#9135, I get the following compiler error while compiling Pelion example with Mbed OS 5.11.2:

[DEBUG] Output: ".\drivers\storage\MySystemStorage.cpp", line 110: Error:  #322: object of abstract class type "NuSDBlockDevice" is not allowed:
[DEBUG] Output:             pure virtual function "mbed::BlockDevice::get_type"  has no overrider

CC @cyliangtw @samchuarm

[cyliangtw]

@screamerbg , about this new virtual function of blockdevice classes, we will implement to fulfill OS 5.12, we will also need to modify the combination of mbed-os.lib and COMPONENT_NUSD.lib in pelion-example-common.

CC @samchuarm

[dannybenor]

Please add this simple function that returns the name of the BD. It is much simpler than revert the changes in 5.11.2.

[cyliangtw]

@dannybenor , it's OK to finish the test by tomorrow.
Next time, it's better to provide one default implementation instead of pure virtual function for backward compatible, for ex return "unknown".