modpost, kallsyms: Treat add '$'-prefixed symbols as mapping symbols

Trying to restrict the '$'-prefix change to RISC-V caused some fallout,
so let's just treat all those symbols as special.

Fixes: c05780ef ("module: Ignore RISC-V mapping symbols too")
Link: https://lore.kernel.org/all/20230712015747.77263-1-wangkefeng.wang@huawei.com/


Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>