target/riscv: Introduce extension implied rule helpers

target/riscv: Introduce extension implied rule helpers

Introduce helpers to enable the extensions based on the implied rules.
The implied extensions are enabled recursively, so we don't have to
expand all of them manually. This also eliminates the old-fashioned
ordering requirement. For example, Zvksg implies Zvks, Zvks implies
Zvksed, etc., removing the need to check the implied rules of Zvksg
before Zvks.

Signed-off-by: Frank Chang <frank.chang@sifive.com>
Reviewed-by: Jerry Zhang Jian <jerry.zhangjian@sifive.com>
Tested-by: Max Chou <max.chou@sifive.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Message-ID: <20240625114629.27793-3-frank.chang@sifive.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>