feat(rme): add ENABLE_RME build option and support for RMM image

The changes include:

- A new build option (ENABLE_RME) to enable FEAT_RME

- New image called RMM. RMM is R-EL2 firmware that manages Realms.
  When building TF-A, a path to RMM image can be specified using
  the "RMM" build flag. If RMM image is not provided, TRP is built
  by default and used as RMM image.

- Support for RMM image in fiptool

Signed-off-by: Zelalem Aweke <zelalem.aweke@arm.com>
Change-Id: I017c23ef02e465a5198baafd665a60858ecd1b25
diff --git a/include/common/bl_common.h b/include/common/bl_common.h
index e33840c..8cb4990 100644
--- a/include/common/bl_common.h
+++ b/include/common/bl_common.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2020, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2021, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -126,6 +126,8 @@
 IMPORT_SYM(uintptr_t, __BL31_END__,		BL31_END);
 #elif defined(IMAGE_BL32)
 IMPORT_SYM(uintptr_t, __BL32_END__,		BL32_END);
+#elif defined(IMAGE_RMM)
+IMPORT_SYM(uintptr_t, __RMM_END__,		RMM_END);
 #endif /* IMAGE_BLX */
 
 /* The following symbols are only exported from the BL2 at EL3 linker script. */