juno/sgm: Maximize space allocated to SCP_BL2

To accommodate the increasing size of the SCP_BL2 binary, the base
address of the memory region allocated to SCP_BL2 has been moved
downwards from its current (mostly) arbitrary address to the beginning
of the non-shared trusted SRAM.

Change-Id: I086a3765bf3ea88f45525223d765dc0dbad6b434
Signed-off-by: Chris Kay <chris.kay@arm.com>
diff --git a/docs/design/firmware-design.rst b/docs/design/firmware-design.rst
index 8297dc7..8e9dc38 100644
--- a/docs/design/firmware-design.rst
+++ b/docs/design/firmware-design.rst
@@ -1859,7 +1859,7 @@
                |   BL2    |  <<<<<<<<<<<<<  |                |
                |----------|  <<<<<<<<<<<<<  |----------------|
                | SCP_BL2  |  <<<<<<<<<<<<<  | BL31 PROGBITS  |
-               |----------|  <<<<<<<<<<<<<  |----------------|
+               |          |  <<<<<<<<<<<<<  |----------------|
                |          |  <<<<<<<<<<<<<  |     BL32       |
                |          |                 +----------------+
                |          |
@@ -1896,7 +1896,7 @@
                |   BL2    |  <<<<<<<<<<<<<  |                |
                |----------|  <<<<<<<<<<<<<  |----------------|
                | SCP_BL2  |  <<<<<<<<<<<<<  | BL31 PROGBITS  |
-               |----------|                 +----------------+
+               |          |                 +----------------+
     0x04001000 +----------+
                |   MHU    |
     0x04000000 +----------+