SST: Implement SST flash on top of CMSIS flash drv

This patch implements SST flash interface on top
of CMSIS flash driver.
It also adds a missing include in sst_utils.h.

Change-Id: I70610584a124d72c2ec6bd911618e0c60e3c7463
Signed-off-by: Marc Moreno <marc.morenoberengue@arm.com>
diff --git a/platform/ext/Mps2AN521.cmake b/platform/ext/Mps2AN521.cmake
index 8dc53a8..a740066 100755
--- a/platform/ext/Mps2AN521.cmake
+++ b/platform/ext/Mps2AN521.cmake
@@ -129,5 +129,12 @@
   message(FATAL_ERROR "Configuration variable BUILD_FLASH (true|false) is undefined!")
 elseif(BUILD_FLASH)
   list(APPEND ALL_SRC_C "${PLATFORM_DIR}/target/mps2/an521/cmsis_drivers/Driver_Flash.c")
+  # There is no real flash memory for code on MPS2 board. Instead a code SRAM is
+  # used for code storage: ZBT SSRAM1. The Driver_Flash driver just emulates a flash
+  # interface and behaviour on top of the SRAM memory.
+  # As the SST area is going to be in RAM, it is required to set SST_RAM_FS to be sure the
+  # SST service knows that when it starts the SST area does not contain any valid block and
+  # it needs  to create an empty one.
+  set(SST_RAM_FS True)
   embedded_include_directories(PATH "${PLATFORM_DIR}/target/mps2/an521/cmsis_drivers" ABSOLUTE)
 endif()