dualroot: add chain of trust for secure partitions

dualroot: add chain of trust for secure partitions

A new certificate "sip-sp-cert" has been added for Silicon Provider(SiP)
owned Secure Partitions(SP). A similar support for Platform owned SP can
be added in future. The certificate is also protected against anti-
rollback using the trusted Non-Volatile counter.

To avoid deviating from TBBR spec, support for SP CoT is only provided
in dualroot.
Secure Partition content certificate is assigned image ID 31 and SP
images follows after it.

The CoT for secure partition look like below.
+------------------+       +-------------------+
| ROTPK/ROTPK Hash |------>| Trusted Key       |
+------------------+       | Certificate       |
                           | (Auth Image)      |
                          /+-------------------+
                         /                   |
                        /                    |
                       /                     |
                      /                      |
                     L                       v
+------------------+       +-------------------+
| Trusted World    |------>| SiP owned SPs     |
| Public Key       |       | Content Cert      |
+------------------+       | (Auth Image)      |
                        /   +-------------------+
                       /                      |
                      /                      v|
+------------------+ L     +-------------------+
| SP_PKG1 Hash     |------>| SP_PKG1           |
|                  |       | (Data Image)      |
+------------------+       +-------------------+
        .                           .
        .                           .
        .                           .
+------------------+       +-------------------+
| SP_PKG8 Hash     |------>| SP_PKG8           |
|                  |       | (Data Image)      |
+------------------+       +-------------------+

Signed-off-by: Manish Pandey <manish.pandey2@arm.com>
Change-Id: Ia31546bac1327a3e0b5d37e8b99c808442d5e53f