KVM: riscv: SBI FWFT: Apply LOCK flag only on successful set

KVM: riscv: SBI FWFT: Apply LOCK flag only on successful set

kvm_sbi_fwft_set() applies the caller's flags to conf->flags before
invoking the set() callback. If the callback returns an error, the LOCK
bit persists and the feature becomes permanently locked without its value
ever being changed.

Move the flags assignment after the callback so LOCK takes effect only
on success.

Fixes: 6b72fd170592 ("RISC-V: KVM: add support for FWFT SBI extension")
Signed-off-by: SeungJu Cheon <suunj1331@gmail.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20260624130238.524706-1-suunj1331@gmail.com
Signed-off-by: Anup Patel <anup@brainfault.org>