KVM: Bail from the dirty ring reset flow if a signal is pending

KVM: Bail from the dirty ring reset flow if a signal is pending

Abort a dirty ring reset if the current task has a pending signal, as the
hard limit of INT_MAX entries doesn't ensure KVM will respond to a signal
in a timely fashion.

Fixes: fb04a1eddb1a ("KVM: X86: Implement ring-based dirty memory tracking")
Reviewed-by: James Houghton <jthoughton@google.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Yan Zhao <yan.y.zhao@intel.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/r/20250516213540.2546077-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>