Remove concept of top/bottom image loading

This concept is no longer required since we now support loading of
images at fixed addresses only.

The image loader now automatically detects the position of the image
inside the current memory layout and updates the layout such that
memory fragmentation is minimised.

The 'attr' field of the meminfo data structure, which used to hold
the bottom/top loading information, has been removed. Also the 'next'
field has been removed as it wasn't used anywhere.

The 'init_bl2_mem_layout()' function has been moved out of common
code and put in BL1-specific code. It has also been renamed into
'bl1_init_bl2_mem_layout'.

Fixes ARM-software/tf-issues#109

Change-Id: I3f54642ce7b763d5ee3b047ad0ab59eabbcf916d
diff --git a/docs/porting-guide.md b/docs/porting-guide.md
index f854af9..b39a62b 100644
--- a/docs/porting-guide.md
+++ b/docs/porting-guide.md
@@ -511,7 +511,7 @@
     the platform to decide where it wants to place the `meminfo` structure for
     BL2.
 
-    BL1 implements the `init_bl2_mem_layout()` function to populate the
+    BL1 implements the `bl1_init_bl2_mem_layout()` function to populate the
     BL2 `meminfo` structure. The platform may override this implementation, for
     example if the platform wants to restrict the amount of memory visible to
     BL2. Details of how to do this are given below.
@@ -574,7 +574,7 @@
 This function helps fulfill requirement 3 above.
 
 
-### Function : init_bl2_mem_layout() [optional]
+### Function : bl1_init_bl2_mem_layout() [optional]
 
     Argument : meminfo *, meminfo *, unsigned int, unsigned long
     Return   : void