feat(measured boot): move init and teardown functions to platform layer

Right now, the measured boot driver is strongly coupled with the TCG
event log driver. It would not be possible to push the measurements
somewhere else, for instance to a physical TPM.

To enable this latter use case, turn the driver's init and teardown
functions into platform hooks. Call them bl2_plat_mboot_init()/finish().
This allows each platform to implement them appropriately, depending on
the type of measured boot backend they use. For example, on a platform
with a physical TPM, the plat_mboot_init() hook would startup the TPM
and setup it underlying bus (e.g. SPI).

Move the current implementation of the init and teardown function to the
FVP platform layer.

Finally move the conditional compilation logic (#if MEASURED_BOOT) out
of bl2_main() to improve its readability. Provide a dummy implementation
in the case measured boot is not included in the build.

Change-Id: Ib6474cb5a9c1e3d4a30c7f228431b22d1a6e85e3
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
7 files changed