[Nucleo-L476RG] Fix available SRAM size

STM32L476xx SRAM is split into two blocks:
• 96 Kbyte mapped at address 0x2000 0000 (SRAM1)
• 32 Kbyte located at address 0x1000 0000 with hardware parity check (SRAM2).

Only the SRAM1 is managed.
One enhancement could be done to use SRAM1 for the heap
and SRAM2 for the stack. (Refer to MBED)


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

Author: fpistm

boards.txt

@@ -282,7 +282,7 @@ Nucleo_64.menu.pnum.NUCLEO_L152RE.build.cmsis_lib_gcc=arm_cortexM3l_math
 Nucleo_64.menu.pnum.NUCLEO_L476RG=Nucleo L476RG
 Nucleo_64.menu.pnum.NUCLEO_L476RG.node=NODE_L476RG
 Nucleo_64.menu.pnum.NUCLEO_L476RG.upload.maximum_size=1048576
-Nucleo_64.menu.pnum.NUCLEO_L476RG.upload.maximum_data_size=131072
+Nucleo_64.menu.pnum.NUCLEO_L476RG.upload.maximum_data_size=98304
 Nucleo_64.menu.pnum.NUCLEO_L476RG.build.mcu=cortex-m4 -mfpu=fpv4-sp-d16 -mfloat-abi=hard
 Nucleo_64.menu.pnum.NUCLEO_L476RG.build.board=NUCLEO_L476RG
 Nucleo_64.menu.pnum.NUCLEO_L476RG.build.series=STM32L4xx