ARM: pxa168: Add board support for gplugD

[Tanmay Upadhyay]

GuruPlug Display (gplugD) is dropped from arch/arm/tools/mach-types as of now.
So, it will not build until it's back in 'mach-types'. For now, one can build
kernel for gplugD by adding below line in arch/arm/tools/mach-types

gplugd                 MACH_SHEEVAD            SHEEVAD                 2625

Patches tested on Linux 2.6.39-rc4 after adding above line in 'mach-types'.