riscv: Safely remove entries from relocation list

Use the safe versions of list and hlist iteration to safely remove
entries from the module relocation lists. To allow mutliple threads to
load modules concurrently, move relocation list pointers onto the stack
rather than using global variables.

Fixes: 8fd6c514 ("riscv: Add remaining module relocations")
Reported-by: Ron Economos <re@w6rz.net>
Closes: https://lore.kernel.org/linux-riscv/444de86a-7e7c-4de7-5d1d-c1c40eefa4ba@w6rz.net


Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
Tested-by: Björn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/r/20231127-module_linking_freeing-v4-1-a2ca1d7027d0@rivosinc.com


Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>