ARM: kirkwood: Add HP T5325 thin client

Convert the kirkwood t5325-setup.c to mostly device tree for
mach-mvebu. Part of the audio setup needs to remain in C for the
moment until suitable bindings are designed and implemented. So add
board code, triggered by the compatibility string.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>