kbuild: Remove 'kmod_' prefix from __KBUILD_MODNAME

kbuild: Remove 'kmod_' prefix from __KBUILD_MODNAME

In preparation for the objtool klp diff subcommand, remove the arbitrary
'kmod_' prefix from __KBUILD_MODNAME and instead add it explicitly in
the __initcall_id() macro.

This change supports the standardization of "unique" symbol naming by
ensuring the non-unique portion of the name comes before the unique
part.  That will enable objtool to properly correlate symbols across
builds.

Cc: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Petr Mladek <pmladek@suse.com>
Tested-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>