Platform: Create shared UART between S and NS

Details:
 - enable test execution on secure side with level 3 isolation
 - add UART related files to secure test client partition
 - add mmio region to secure test client partition to access shared UART
 - avoid PPC configuration for standard UART as it is a shared resource
   between S and NS and not secure only
 - add libc_nano.a to secure app in case of GCC to have printf support
 - move heap area to be part of secure test client data area,
   because GCC printf implementation uses heap

Change-Id: I146f32b234451f9d75db04aacffd152c2e2d3565
Signed-off-by: Tamas Ban <tamas.ban@arm.com>
24 files changed