MLECO-3070: Further HAL cleanup.

Cleaning up HAL sources by removing unnecessary redirections
with function pointers. The "platform packages" under HAL are
now streamlined enough to not need any major HAL wrapping (as
was the case before).

This allows us to have a very thin HAL layer that sits on top
of the platform and compnent packs. Also helps in getting rid
of "hal platform" pointer being passed around in the code to
use any HAL functionality.

Change-Id: I04b2057f972aad7a5cfb4a396bcdf147c9f9ef1c
Signed-off-by: Kshitij Sisodia <kshitij.sisodia@arm.com>