qemu: remove unused BL32_SIZE

I do not see any line that references BL32_SIZE.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/plat/qemu/include/platform_def.h b/plat/qemu/include/platform_def.h
index d983ce6..1fa2164 100644
--- a/plat/qemu/include/platform_def.h
+++ b/plat/qemu/include/platform_def.h
@@ -175,7 +175,6 @@
 #else
 # error "Unsupported BL32_RAM_LOCATION_ID value"
 #endif
-#define BL32_SIZE			(BL32_LIMIT - BL32_BASE)
 
 #define NS_IMAGE_OFFSET			0x60000000