Ramdisk loading code, including initrd_high variable handling,
was duplicated for PPC and M68K platforms. This patch creates
common helper routine that is being called from both platform
do_bootm_linux() routines.
Signed-off-by: NMarian Balakowicz <m8@semihalf.com>

Architecture specific do_bootm_linux() routines share common
ramdisk image processing code. Move this code to a common
helper routine.
Signed-off-by: NMarian Balakowicz <m8@semihalf.com>

Move numeric-id to name translation for image os/arch/type/comp header
fields to a helper routines: image_get_os_name(), image_get_arch_name(),
image_get_type_name(), image_get_comp_name().
Signed-off-by: NMarian Balakowicz <m8@semihalf.com>

- use single image header pointer instead of a set of auxilliary variables.
- add multi component image helper routines: get component size/data address
Signed-off-by: NMarian Balakowicz <m8@semihalf.com>

Move common, watchdog sensible memmove code to a helper memmmove_wd() routine.
Signed-off-by: NMarian Balakowicz <m8@semihalf.com>

- Add inline helper macros for basic header processing
- Move common non inline code common/image.c
- Replace direct header access with the API routines
- Rename IH_CPU_* to IH_ARCH_*
Signed-off-by: NMarian Balakowicz <m8@semihalf.com>