target/riscv/kvm: fix leak in kvm_riscv_init_multiext_cfg()

target/riscv/kvm: fix leak in kvm_riscv_init_multiext_cfg()

'reglist' is being g-malloc'ed but never freed.

Reported-by: Andrew Jones <ajones@ventanamicro.com>
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: <20250429124421.223883-3-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Cc: qemu-stable@nongnu.org
(cherry picked from commit 906af6de9462c5192547cca0beac2c134659a437)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>