drivers/fsl-mc: Make MC boot error messages more readable

Make it easier for the user to notice when the MC firmware
had problems booting.

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