refactor(build): renaming BL2_AT_EL3 to RESET_TO_BL2

Along with e09da7be3fe5f7a59f16abc6008a8a97c3e1c247 that introduces a
breaking refactoring change we have to rename the build option in the CI
scripts.
Renaming BL2_AT_EL3 to RESET_TO_BL2.

Signed-off-by: Maksims Svecovs <maksims.svecovs@arm.com>
Change-Id: I57fe6c8e289a71d8d3cea3a6d71760d7df43112e
diff --git a/script/build_package.sh b/script/build_package.sh
index dcbd9e5..d219528 100755
--- a/script/build_package.sh
+++ b/script/build_package.sh
@@ -438,7 +438,7 @@
 		"$(get_tf_opt RESET_TO_BL31)" | \
 		"$(get_tf_opt ARM_LINUX_KERNEL_AS_BL33)" | \
 		"$(get_tf_opt RESET_TO_SP_MIN)" | \
-		"$(get_tf_opt BL2_AT_EL3)")
+		"$(get_tf_opt RESET_TO_BL2)")
 			return 0;;
 	esac