Fix all the system image sizes.

x86 just bit me. I did manage to build mips today, but I assume it
can't be long before we hit the limit there too if every other target
has hit it already.

Change-Id: I28dfe3b4f9565cb79e0bf6b0ffc55a9d6e64a9b0
diff --git a/target/board/generic_mips/BoardConfig.mk b/target/board/generic_mips/BoardConfig.mk
index e66ade1..17e241d 100644
--- a/target/board/generic_mips/BoardConfig.mk
+++ b/target/board/generic_mips/BoardConfig.mk
@@ -50,7 +50,7 @@
 USE_OPENGL_RENDERER := true
 
 TARGET_USERIMAGES_USE_EXT4 := true
-BOARD_SYSTEMIMAGE_PARTITION_SIZE := 681574400
+BOARD_SYSTEMIMAGE_PARTITION_SIZE := 786432000
 BOARD_USERDATAIMAGE_PARTITION_SIZE := 576716800
 BOARD_CACHEIMAGE_PARTITION_SIZE := 69206016
 BOARD_CACHEIMAGE_FILE_SYSTEM_TYPE := ext4