refactor(gpt): productize and refactor GPT library

This patch updates and refactors the GPT library and fixes bugs.

- Support all combinations of PGS, PPS, and L0GPTSZ parameters.
- PPS and PGS are set at runtime, L0GPTSZ is read from GPCCR_EL3.
- Use compiler definitions to simplify code.
- Renaming functions to better suit intended uses.
- MMU enabled before GPT APIs called.
- Add comments to make function usage more clear in GPT library.
- Added _rme suffix to file names to differentiate better from the
  GPT file system code.
- Renamed gpt_defs.h to gpt_rme_private.h to better separate private
  and public code.
- Renamed gpt_core.c to gpt_rme.c to better conform to TF-A precedent.

Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: I4cbb23b0f81e697baa9fb23ba458aa3f7d1ed919
diff --git a/lib/gpt_rme/gpt_rme.mk b/lib/gpt_rme/gpt_rme.mk
new file mode 100644
index 0000000..60176f4
--- /dev/null
+++ b/lib/gpt_rme/gpt_rme.mk
@@ -0,0 +1,8 @@
+#
+# Copyright (c) 2021, Arm Limited. All rights reserved.
+#
+# SPDX-License-Identifier: BSD-3-Clause
+#
+
+GPT_LIB_SRCS	:=	$(addprefix lib/gpt_rme/,        \
+			gpt_rme.c)