refactor(measured-boot): avoid Measured-Boot dependency on Trusted-Boot

Measured-Boot and Trusted-Boot are orthogonal to each other and hence
removed dependency of Trusted-Boot on Measured-Boot by making below
changes -
1. BL1 and BL2 main functions are used for initializing Crypto module
   instead of the authentication module
2. Updated Crypto module registration macro for MEASURED_BOOT with only
   necessary callbacks for calculating image hashes
3. The 'load_auth_image' function is now used for the image measurement
   during Trusted or Non-Trusted Boot flow

Change-Id: I3570e80bae8ce8f5b58d84bd955aa43e925d9fff
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
diff --git a/docs/getting_started/build-options.rst b/docs/getting_started/build-options.rst
index d77875e..a34bb3c 100644
--- a/docs/getting_started/build-options.rst
+++ b/docs/getting_started/build-options.rst
@@ -529,9 +529,9 @@
    the build. The default value is 40 in debug builds and 20 in release builds.
 
 -  ``MEASURED_BOOT``: Boolean flag to include support for the Measured Boot
-   feature. If this flag is enabled ``TRUSTED_BOARD_BOOT`` must be set as well
-   in order to provide trust that the code taking the measurements and recording
-   them has not been tampered with.
+   feature. This flag can be enabled with ``TRUSTED_BOARD_BOOT`` in order to
+   provide trust that the code taking the measurements and recording them has
+   not been tampered with.
 
    This option defaults to 0.