Fix wrong f_cpu values thanks @knielsen

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

Author: fpistm

boards.txt

@@ -94,7 +94,7 @@ Nucleo_64.menu.pnum.NUCLEO_F091RC.node=NODE_F091RC
 Nucleo_64.menu.pnum.NUCLEO_F091RC.upload.maximum_size=262144
 Nucleo_64.menu.pnum.NUCLEO_F091RC.upload.maximum_data_size=32768
 Nucleo_64.menu.pnum.NUCLEO_F091RC.build.mcu=cortex-m0
-Nucleo_64.menu.pnum.NUCLEO_F091RC.build.f_cpu=8000000L
+Nucleo_64.menu.pnum.NUCLEO_F091RC.build.f_cpu=48000000L
 Nucleo_64.menu.pnum.NUCLEO_F091RC.build.board=NUCLEO_F091RC
 Nucleo_64.menu.pnum.NUCLEO_F091RC.build.series=STM32F0xx
 Nucleo_64.menu.pnum.NUCLEO_F091RC.build.product_line=STM32F091xC
@@ -122,7 +122,7 @@ Nucleo_64.menu.pnum.NUCLEO_F303RE.node=NODE_F303RE
 Nucleo_64.menu.pnum.NUCLEO_F303RE.upload.maximum_size=524288
 Nucleo_64.menu.pnum.NUCLEO_F303RE.upload.maximum_data_size=65536
 Nucleo_64.menu.pnum.NUCLEO_F303RE.build.mcu=cortex-m4 -mfpu=fpv4-sp-d16 -mfloat-abi=hard
-Nucleo_64.menu.pnum.NUCLEO_F303RE.build.f_cpu=8000000L
+Nucleo_64.menu.pnum.NUCLEO_F303RE.build.f_cpu=72000000L
 Nucleo_64.menu.pnum.NUCLEO_F303RE.build.board=NUCLEO_F303RE
 Nucleo_64.menu.pnum.NUCLEO_F303RE.build.series=STM32F3xx
 Nucleo_64.menu.pnum.NUCLEO_F303RE.build.product_line=STM32F303xE