Add a dummy command to the all: rule in sub-makefiles.
This avoids "Nothing to be done for `all'." messages from make.
Signed-off-by: NPaul Brook <paul@codesourcery.com>

From Paul Brook:

 "the fdc is tied to the ISA DMA engine. We don't currently have a target
  independent method of handling inter-device data transfer."
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

Signed-off-by: NBlue Swirl <blauwirbel@gmail.com>

Signed-off-by: Nmalc <av1474@comtv.ru>

The only target dependency for most hardware is sizeof(target_phys_addr_t).
Build these files into a convenience library, and use that instead of
building for every target.

Remove and poison various target specific macros to avoid bogus target
dependencies creeping back in.

Big/Little endian is not handled because devices should not know or care
about this to start with.
Signed-off-by: NPaul Brook <paul@codesourcery.com>