uniphier: make all BL images completely position-independent

This platform supports multiple SoCs. The next SoC will still keep
quite similar architecture, but the memory base will be changed.

The ENABLE_PIE improves the maintainability and usability. You can reuse
a single set of BL images for other SoC/board without re-compiling TF-A
at all. This will also keep the code cleaner because it avoids #ifdef
around various base addresses.

By defining ENABLE_PIE, BL2_AT_EL3, BL31, and BL32 (TSP) are really
position-independent now. You can load them anywhere irrespective of
their link address.

Change-Id: I8d5e3124ee30012f5b3bfa278b0baff8efd2fff7
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/plat/socionext/uniphier/platform.mk b/plat/socionext/uniphier/platform.mk
index 3c74fe6..8e96b68 100644
--- a/plat/socionext/uniphier/platform.mk
+++ b/plat/socionext/uniphier/platform.mk
@@ -9,6 +9,9 @@
 override PROGRAMMABLE_RESET_ADDRESS	:= 1
 override USE_COHERENT_MEM		:= 1
 override ENABLE_SVE_FOR_NS		:= 0
+
+# Disabling ENABLE_PIE saves memory footprint a lot, but you need to adjust
+# UNIPHIER_MEM_BASE so that all TF images are loaded at their link addresses.
 override ENABLE_PIE			:= 1
 
 # Cortex-A53 revision r0p4-51rel0