fix(bl1): add missing `__RW_{START,END}__` symbols

These symbols are missing from BL1, which causes undefined reference
errors when linking with LTO enabled.

Change-Id: Id3eda0550c957f5ef0535f0de4ff2ad87c93b82a
Signed-off-by: Chris Kay <chris.kay@arm.com>

bl1/bl1.ld.S

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2023, Arm Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2024, Arm Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -116,6 +116,8 @@ SECTIONS {
     ASSERT(BL1_RW_BASE == ALIGN(PAGE_SIZE),
         "BL1_RW_BASE address is not aligned on a page boundary.")
 
+    __RW_START__ = .;
+
     DATA_SECTION >RAM AT>ROM
 
     __DATA_RAM_START__ = __DATA_START__;
@@ -148,6 +150,8 @@ SECTIONS {
     } >RAM
 #endif /* USE_COHERENT_MEM */
 
+    __RW_END__ = .;
+
     __BL1_RAM_START__ = ADDR(.data);
     __BL1_RAM_END__ = .;