drivers/fsl-mc: Changed MC firmware loading for new boot architecture

Changed MC firmware loading to comply with the new MC boot architecture.
Flush D-cache hierarchy after loading MC images. Add environment
variables "mcboottimeout" for MC boot timeout in milliseconds,
"mcmemsize" for MC DRAM block size. Check MC boot status before calling
flib functions.

Signed-off-by: J. German Rivera <German.Rivera@freescale.com>
Signed-off-by: York Sun <yorksun@freescale.com>