hw/i3c/core: Initialize num_sent in i3c_send_byte()

i3c_send_byte() declared num_sent without initializing it before passing its address to i3c_send(). Although i3c_send_byte() itself ignores num_sent after the call, i3c_send() forwards it to trace_i3c_send(). If the target send callback does not set *num_sent, the trace may print an uninitialized value, leading to misleading or garbage output. Example concern from review: trace_i3c_send(*num_sent, num_to_send, ret == 0); If *num_sent is not written by the callback, this trace can report an incorrect number of transmitted bytes. Initialize num_sent to 0 to ensure deterministic and predictable trace output, even if the callback fails to update it. Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com> Reviewed-by: Jithu Joseph <jithu.joseph@oss.qualcomm.com> Link: https://lore.kernel.org/qemu-devel/20260303013322.1297499-4-jamin_lin@aspeedtech.com Signed-off-by: Cédric Le Goater <clg@redhat.com>