kexec_file, x86: move re-factored code to generic side

kexec_file, x86: move re-factored code to generic side

In the previous patches, commonly-used routines, exclude_mem_range() and
prepare_elf64_headers(), were carved out.  Now place them in kexec
common code.  A prefix "crash_" is given to each of their names to avoid
possible name collisions.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: AKASHI Takahiro <[email protected]>
Acked-by: Dave Young <[email protected]>
Tested-by: Dave Young <[email protected]>
Cc: Vivek Goyal <[email protected]>
Cc: Baoquan He <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>