STM32 unit test failures

[tmiw]

The following failures were discovered on main during work on #12:

The following tests FAILED:
	  5 - tst_ofdm_mod_plain (Failed)
	  6 - tst_ofdm_mod_ldpc (Failed)
	  7 - tst_ofdm_demod_quick (Failed)
	  8 - tst_ofdm_demod_ideal (Failed)
	  9 - tst_ofdm_demod_AWGN (Failed)
	 10 - tst_ofdm_demod_fade (Failed)
	 11 - tst_ofdm_demod_ldpc (Failed)
	 14 - tst_codec2_enc_1300 (Failed)
	 15 - tst_codec2_enc_700C (Failed)
	 21 - tst_api_mod_700E_CODEC (Failed)

(Note: these were run on a NUCLEO-F446RE dev board.)

More detailed test output at stm32-ctest-log.txt.

[drowe67]

Note for FreeDV PLT - no further action on this from FreeDV team members as 700D will soon be obsolete.