target/riscv/tcg: add hash table insert helpers

target/riscv/tcg: add hash table insert helpers

Previous patches added several g_hash_table_insert() patterns. Add two
helpers, one for each user hash, to make the code cleaner.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20231218125334.37184-15-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>