build(bl2): enable SP pkg loading for S-EL1 SPMC

Currently the SP package loading mechanism is only enabled when S-EL2
SPMC is selected. Remove this limitation.

Signed-off-by: Balint Dobszay <balint.dobszay@arm.com>
Change-Id: I5bf5a32248e85a26d0345cacff7d539eed824cfc
diff --git a/make_helpers/defaults.mk b/make_helpers/defaults.mk
index c188621..f26cab6 100644
--- a/make_helpers/defaults.mk
+++ b/make_helpers/defaults.mk
@@ -32,6 +32,9 @@
 # Execute BL2 at EL3
 BL2_AT_EL3			:= 0
 
+# Only use SP packages if SP layout JSON is defined
+BL2_ENABLE_SP_LOAD		:= 0
+
 # BL2 image is stored in XIP memory, for now, this option is only supported
 # when BL2_AT_EL3 is 1.
 BL2_IN_XIP_MEM			:= 0