fix(cm): hide `cm_init_context_by_index` from BL1

BL1 requires the context management library but does not use or
implement `cm_init_context_by_index`. This change ensures that is not
compiled into BL1, as linking with LTO enabled causes an undefined
reference for this function.

Change-Id: I4a4602843bd75bc4f47b3e0c4c5a6efce1514ef6
Signed-off-by: Chris Kay <chris.kay@arm.com>
diff --git a/lib/el3_runtime/aarch64/context_mgmt.c b/lib/el3_runtime/aarch64/context_mgmt.c
index 39f3947..6d98860 100644
--- a/lib/el3_runtime/aarch64/context_mgmt.c
+++ b/lib/el3_runtime/aarch64/context_mgmt.c
@@ -809,6 +809,7 @@
 #endif /* IMAGE_BL31 */
 }
 
+#if !IMAGE_BL1
 /*******************************************************************************
  * The following function initializes the cpu_context for a CPU specified by
  * its `cpu_idx` for first use, and sets the initial entrypoint state as
@@ -821,6 +822,7 @@
 	ctx = cm_get_context_by_index(cpu_idx, GET_SECURITY_STATE(ep->h.attr));
 	cm_setup_context(ctx, ep);
 }
+#endif /* !IMAGE_BL1 */
 
 /*******************************************************************************
  * The following function initializes the cpu_context for the current CPU