module: do not pass opaque pointer for symbol search

There is no need to use an opaque pointer for check_exported_symbol()
or find_exported_symbol_in_section.

Pass (struct find_symbol_arg *) explicitly.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>