linux: Add version 3.17 compatible with all IGEP boards.

Kernel 3.17 is compatible with igep0020, igep0030 and igep0033 machines.

Signed-off-by: Enric Balletbo i Serra <eballetbo@gmail.com>
linux-igep: Set DEFAULT_PREFERENCE to -1

Kernel 3.17 is the kernel preferably.

Signed-off-by: Enric Balletbo i Serra <eballetbo@gmail.com>
u-boot: update to 2014.10 version.

Update to the latest published u-boot version.

Signed-off-by: Enric Balletbo i Serra <eballetbo@gmail.com>
README: Add instructions for all different machines.

  o Machine configuration for the IGEPv2 AM/DM37x Processor Board
    MACHINE ?= "igep0020"

  o Machine configuration for the IGEP COM MODULE AM/DM37x Processor Board
    MACHINE ?= "igep0030"

  o Machine configuration for the IGEP COM AQUILA AM335x Processor Board
    MACHINE ?= "igep0033"

Signed-off-by: Enric Balletbo i Serra <eballetbo@gmail.com>