Apply TBBR naming convention to the fip_create options

Apply TBBR naming convention to the fip_create options

The fip_create tool specifies images in the command line using the
ARM TF naming convention (--bl2, --bl31, etc), while the cert_create
tool uses the TBBR convention (--tb-fw, --soc-fw, etc). This double
convention is confusing and should be aligned.

This patch updates the fip_create command line options to follow the
TBBR naming convention. Usage examples in the User Guide have been
also updated.

NOTE: users that build the FIP by calling the fip_create tool directly
from the command line must update the command line options in their
scripts. Users that build the FIP by invoking the main ARM TF Makefile
should not notice any difference.

Change-Id: I84d602630a2585e558d927b50dfde4dd2112496f