Fix warnings due to unused variables, comparison between signed and
unsigned. This patch also re-enables I2C asserts that were disabled
during early development.
Bring all the FPGA CI Test Shield C and C++ driver files into mbed-os
as the component FPGA_CI_TEST_SHIELD. When this component is enabled
all the files that are needed to communicate with, update firmware on
and run testing with the FPGA are built.