Platform: Don't overlay TFM_SHARED_DATA and ARM_LIB_STACK

ARM_LIB_STACK may grow large enough to overwrite TFM_SHARED_DATA before
TFM_SHARED_DATA is read by partitions during partitions init process.
Thus, don't overlay these two linker regions to avoid this problem.

This is not a problem for GCC and IAR as they don't overlay the two
regions.

Signed-off-by: Bohdan Hunko <Bohdan.Hunko@infineon.com>
Change-Id: I24df1ca84a3d65c60685bc1b239bd57e9a24b1b4