chore(g4): define HSE_VALUE of the Nucleo G431RB

Signed-off-by: Frederic Pillon <frederic.pillon@st.com>

Author: fpistm

variants/STM32G4xx/G431R(6-8)(I-T)_G431RB(I-T)x(Z)_G441RB(I-T)/variant_NUCLEO_G431RB.h

@@ -172,6 +172,7 @@
   #define HAL_DAC_MODULE_ENABLED
 #endif
 
+#define HSE_VALUE               24000000
 /*----------------------------------------------------------------------------
  *        Arduino objects - C++ only
  *----------------------------------------------------------------------------*/