arm: Kirkwood: Basic SOCs support

Kirkwood family controllers are highly integrated SOCs
based on Feroceon-88FR131/Sheeva-88SV131/arm926ejs cpu core.

SOC versions supported:-
1) 88F6281-A0       define CONFIG_KW88F6281_A0
2) 88F6192-A0       define CONFIG_KW88F6192_A0

Other supported features:-
1) get_random_hex() fucntion
2) PCI Express port initialization
3) NS16550 driver support

Contributors:
Yotam Admon <yotam@marvell.com>
Michael Blostein <michaelbl@marvell.com

Reviewed-by: Ronen Shitrit <rshitrit@marvell.com>
Acked-by: Stefan Rose <sr@denx.de>
Signed-off-by: Prafulla Wadaskar <prafulla@marvell.com>