target/riscv/kvm: set 'aia_mode' to default in error path

target/riscv/kvm: set 'aia_mode' to default in error path

When failing to set the selected AIA mode, 'aia_mode' is left untouched.
This means that 'aia_mode' will not reflect the actual AIA mode,
retrieved in 'default_aia_mode',

This is benign for now, but it will impact QMP query commands that will
expose the 'aia_mode' value, retrieving the wrong value.

Set 'aia_mode' to 'default_aia_mode' if we fail to change the AIA mode
in KVM.

While we're at it, rework the log/warning messages to be a bit less
verbose. Instead of:

KVM AIA: default mode is emul
qemu-system-riscv64: warning: KVM AIA: failed to set KVM AIA mode

We can use a single warning message:

qemu-system-riscv64: warning: KVM AIA: failed to set KVM AIA mode 'auto', using default host mode 'emul'

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20241028182037.290171-2-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
(cherry picked from commit d201a127e164b1683df5e7c93c6d42a74122db99)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>