Parse the parameter structure the FSBL populates, to populate the bl32
and bl33 image structures.

Cc: Sarat Chand Savitala <saratcha@xilinx.com>
Cc: petalinux-dev@xilinx.com
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
[ SB
 - pass pointers to structs instead of structs
 - handle execution state parameter
 - populate bl32 SPSR
 - add documentation
 - query bootmode and consider missing handoff parameters an error when
   not in JTAG boot mode
]
Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>