loader: Add AddressSpace loading support to targphys

loader: Add AddressSpace loading support to targphys

Add a new function load_image_targphys_as() that allows the caller
to specify an AddressSpace to use when loading a targphys. The
original load_image_targphys() function doesn't have any change in
functionality.

Signed-off-by: Alistair Francis <alistair.francis@xilinx.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 87de45de7acf02cbe6bae9d6c4d6fb8f3aba4f61.1474331683.git.alistair.francis@xilinx.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>