Fix compile failure with non modular builds

Commit deac93df26b20cf8438339b5935b5f5643bc30c9 ("lib: Correct printk
%pF to work on all architectures") broke the non modular builds by
moving an essential function into modules.c.  Fix this by moving it
out again and into asm/sections.h as an inline.  To do this, the
definition of struct ppc64_opd_entry has been lifted out of modules.c
and put in asm/elf.h where it belongs.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>