fsl_ifc: add support for different IFC bank count

Calculate reserved fields according to IFC bank count

1. Move csor_ext register behind csor register and fix res offset
2. Move ifc bank count to config_mpc85xx.h to support 8 bank count
3. Guard fsl_ifc.h with CONFIG_FSL_IFC macro to eliminate the compile
   error on some devices that does not have IFC controller.

Signed-off-by: Mingkai Hu <Mingkai.hu@freescale.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>