Currently only single signing domain is supported for SP packages but
there is plan to support dual signing domains if CoT is dualroot.

SP_CONTENT_CERT_ID is the certificate file which is currently generated
and signed with trusted world key which in-turn is derived from Silicon
provider RoT key.
To allow dual signing domain for SP packages, other certificate file
will be derived from Platform owned RoT key.

This patch renames "SP_CONTENT_CERT_ID" to "SIP_SP_CONTENT_CERT_ID" and
does other related changes.

Signed-off-by: Manish Pandey <manish.pandey2@arm.com>
Change-Id: I0bc445a3ab257e2dac03faa64f46e36a9fed5e93

with sha 44f1aa8, support for Silicon Provider(SiP) owned Secure
Partition(SP) was added for dualroot CoT. This patch extends this
support for tbbr CoT.

Earlier tbbr CoT for SPs was left to avoid adding new image types in
TBBR which could possibly be seen as deviation from specification.
But with further discussions it is understood that TBBR being a
*minimal* set of requirements that can be extended as long as we don't
violate any of the musts, which is the case with adding SP support.

Signed-off-by: Manish Pandey <manish.pandey2@arm.com>
Change-Id: I1b9e3ebdd7d653f1fd4cc3bd910a69871b55ecbb

CoT used for BL1 and BL2 are moved to tbbr_cot_bl1.c
and tbbr_cot_bl2.c respectively.
Common CoT used across BL1 and BL2 are moved to
tbbr_cot_common.c.

Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
Change-Id: I2252ac8a6960b3431bcaafdb3ea4fb2d01b79cf5