powerpc/p4080: Add support for secure boot flow

Pre u-boot Flow:
1. User loads the u-boot image in flash
2. PBL/Configuration word is used to create LAW for Flash at 0xc0000000
   (Please note that ISBC expects all these addresses, images to be
    validated, entry point etc within 0 - 3.5G range)
3. ISBC validates the u-boot image, and passes control to u-boot
   at 0xcffffffc.

Changes in u-boot:
1. Temporarily map CONFIG_SYS_MONITOR_BASE to the 1M
   CONFIG_SYS_PBI_FLASH_WINDOW in AS=1.
   (The CONFIG_SYS_PBI_FLASH_WINDOW is the address map for the flash
    created by PBL/configuration word within 0 - 3.5G memory range. The
    u-boot image at this address has been validated by ISBC code)
2. Remove TLB entries for 0 - 3.5G created by ISBC code
3. Remove the LAW entry for the CONFIG_SYS_PBI_FLASH_WINDOW created by
   PBL/configuration word after switch to AS = 1

Signed-off-by: Ruchika Gupta <ruchika.gupta@freescale.com>
Signed-off-by: Kuldip Giroh <kuldip.giroh@freescale.com>
Acked-by: Wood Scott-B07421 <B07421@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>