udoo: Move and optimize platform register setting.

Previous uDoo configuration adopts register settings for DDR3, clock, muxing,
etc. taken from Nitrogen6x. uDoo schematics is rather different from that board,
and it needs customized setting for most of the registers.
All this changes can be considered atomical since it is part of initial support
of the board.

Patch changes uDoo configuration files path to a specific one, and adopt
optimized value for every configured register.

Signed-off-by: Giuseppe Pagano <giuseppe.pagano@seco.com>
Tested-by: Fabio Estevam <fabio.estevam@freescale.com>
CC: Stefano Babic <sbabic@denx.de>
CC: Fabio Estevam <fabio.estevam@freescale.com>