powerpc/mpc85xx: Add DSP side awareness for Freescale Heterogeneous SoCs

The code provides framework for heterogeneous multicore chips based on StarCore
and Power Architecture which are chasis-2 compliant, like B4860 and B4420

It will make u-boot recognize all non-ppc cores and peripherals like
SC3900/DSP CPUs, MAPLE, CPRI and print their configuration in u-boot logs.
Example boot logs of B4860QDS:

U-Boot 2015.01-00232-geef6e36-dirty (Jan 19 2015 - 11:58:45)

CPU0: B4860E, Version: 2.2, (0x86880022)
Core: e6500, Version: 2.0, (0x80400120)
Clock Configuration:
CPU0:1600 MHz, CPU1:1600 MHz, CPU2:1600 MHz, CPU3:1600 MHz,
DSP CPU0:1200 MHz, DSP CPU1:1200 MHz, DSP CPU2:1200 MHz, DSP CPU3:1200 MHz,
DSP CPU4:1200 MHz, DSP CPU5:1200 MHz,
CCB:666.667 MHz,
DDR:933.333 MHz (1866.667 MT/s data rate) (Asynchronous), IFC:166.667 MHz
CPRI:600 MHz
MAPLE:600 MHz, MAPLE-ULB:800 MHz, MAPLE-eTVPE:1000 MHz
FMAN1: 666.667 MHz
QMAN: 333.333 MHz

Top level changes include:
(1) Top level CONFIG to identify HETEROGENUOUS clusters
(2) CONFIGS for SC3900/DSP components
(3) Global structures like "cpu_type" and "MPC85xx_SYS_INFO"
updated for dsp cores and other components
(3) APIs to get DSP num cores and their Mask like:
cpu_dsp_mask, cpu_num_dspcores etc same as that of PowerPC
(5) Code to fetch and print SC cores and other heterogenous
device's frequencies
(6) README added for the same

Signed-off-by: Shaveta Leekha <shaveta@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>