mbed: Fix compile error due to missing FixedMessageQueue
mbed: Fix compile error due to missing FixedMessageQueue

Regression since some 10 commits back

rraallvv/microflo,microflo/microflo,rraallvv/microflo,microflo/microflo,microflo/microflo,microflo/microflo,rraallvv/microflo,microflo/microflo,microflo/microflo,rraallvv/microflo