powerpc/p2041rdb: Add p2041rdb board support

P2041RDB Specification:
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Memory subsystem:
 * 4Gbyte unbuffered DDR3 SDRAM SO-DIMM(64bit bus)
 * 128 Mbyte NOR flash single-chip memory
 * 256 Kbit M24256 I2C EEPROM
 * 16 Mbyte SPI memory
 * SD connector to interface with the SD memory card

Ethernet:
 * dTSEC1: connected to the Vitesse SGMII PHY (VSC8221)
 * dTSEC2: connected to the Vitesse SGMII PHY (VSC8221)
 * dTSEC3: connected to the Vitesse SGMII PHY (VSC8221)
 * dTSEC4: connected to the Vitesse RGMII PHY (VSC8641)
 * dTSEC5: connected to the Vitesse RGMII PHY (VSC8641)

PCIe:
 * Lanes E, F, G and H of Bank1 are connected to one x4 PCIe SLOT1
 * Lanes C and Land D of Bank2 are connected to one x4 PCIe SLOT2

SATA: Lanes C and Land D of Bank2 are connected to two SATA connectors

USB 2.0: connected via a internal UTMI PHY to two TYPE-A interfaces

I2C:
 * I2C1: Real time clock, Temperature sensor, Memory module
 * I2C2: Vcore Regulator, 256Kbit I2C Bus EEPROM, PCIe slot1/2

UART: supports two UARTs up to 115200 bps for console

Signed-off-by: Mingkai Hu <Mingkai.hu@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>