Revert "module: remove the SHF_ALLOC flag on the __versions section."

Revert "module: remove the SHF_ALLOC flag on the __versions section."

This reverts commit 9cb610d8e35fe3ec95a2fe2030b02f85aeea83c1.

This was an impressively stupid patch.  Firstly, we reset the SHF_ALLOC
flag lower down in the same function, so the patch was useless.  Even
better, find_sec() ignores sections with SHF_ALLOC not set, so
it breaks CONFIG_MODVERSIONS=y with CONFIG_MODULE_FORCE_LOAD=n, which
refuses to load the module since it can't find the __versions section.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>