[u-boot] Move U-boot environment config

Move the u-boot environment configuration file for Overo to a
generic location as it is not typically dependent on the particular
version of u-boot.

Signed-off-by: Ash Charles <ashcharles@gmail.com>
[u-boot] Update to u-boot v2014.04 for Pepper

Signed-off-by: Ash Charles <ashcharles@gmail.com>
[linux] Move boot logo to shared location

The boot logo (logo_linux_clut224-generic.ppm) is not kernel-specific
so it can be stored in a shared location.

Signed-off-by: Ash Charles <ashcharles@gmail.com>
[linux] Update Pepper kernel to 3.14.4

The Pepper SBC boots using a 3.14.4-based device tree kernel.

Signed-off-by: Ash Charles <ashcharles@gmail.com>