migration: Fix migration failure when aia is configured as aplic-imsic

migration: Fix migration failure when aia is configured as aplic-imsic

Address an error in migration when aia is configured as 'aplic-imsic' in
riscv kvm vm by adding riscv_aplic_state_needed() and
riscv_imsic_state_needed() to determine whether the corresponding sates are
needed.

Previously, the fields in the vmsds of 'riscv_aplic' and 'riscv_imsic' can
only be initialized under certain special conditions in commit 95a97b3fd2.
However, the corresponding ses of these vmsds are inserted into the
savevm_state.handlers unconditionally. This led to migration failure
characterized by uninitialized fields when save vm state:
qemu-system-riscv64: ../migration/vmstate.c:433: vmstate_save_state_v:
Assertion 'first_elem || !n_elems || !size' failed.

Fixes: 95a97b3fd2 ("target/riscv: update APLIC and IMSIC to support KVM AIA")
Signed-off-by: Xuemei Liu <liu.xuemei1@zte.com.cn>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20250616150034827wuHs_ffe3Qm8cqFXT7HeW@zte.com.cn>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>