kmod/core: convert undefined module relas to dynrelas

When patching module A, if one of the new function's relas reference a
symbol in module B, we currently just leave it as a normal rela.  But if
module B hasn't been loaded yet, the patch module will fail to load due
to the rela's reference to an undefined symbol.

The fix is to convert these relas to dynrelas, which can be resolved
later in the module notifier when A is loaded.

Also added support for the R_X86_64_NONE relocation type, needed for
dynrelas which reference __fentry__.