loader: fix elf lookup_symbol type filtering

The existing logic doesn't seem to make much sense, as we won't filter
on the type if st_shndx != SHN_UNDEF. In practice, this breaks booting
12.3 kerne

loader: fix elf lookup_symbol type filtering

The existing logic doesn't seem to make much sense, as we won't filter
on the type if st_shndx != SHN_UNDEF. In practice, this breaks booting
12.3 kernels on newer loaders, as they do have a `kernphys` symbol of
the wrong type (NOTYPE, rather than OBJECT) -- we end up deriving the
wrong value for copy_staging.

It's unclear if this version makes any more sense, but it seems to match
what rtld's matched_symbol() does. Loader doesn't need to care about
STT_FUNC w/ UND shndx, because we won't encounter those; in kmods,
undefined (kernel) functions are NOTYPE.

Approved by: so
Security: FreeBSD-EN-22:27.loader
Reported by: Christian McDonald <cmcdonald netgate com>
Reviewed by: imp, kib, tsoome

(cherry picked from commit 0701dbda94f21de8ddab3113f79262a26cc7b96c)
(cherry picked from commit 2b31059ea701957584e68a75857206d80a230211)

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