The fiptool and cert_create use the same command options for images.
It is pretty easy to handle both in the same, symmetrical way.

Move CRT_ARGS and CRT_DEPS to FIP_ADD_PAYLOAD.  This refactoring makes
sense because FIP_ADD_PAYLOAD is called from MAKE_BL (when building
images from source), and from FIP_ADD_IMG (when including external
images).  (FIP_ADD_PAYLOAD will be renamed later on since it now
caters to both fiptool and cert_create).

We can delete CERT_ADD_CMD_OPT for images in tbbr.mk.  It still
needs to call CERT_ADD_CMD_OPT directly for certificates.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>