bulk: set ->size of last bulk_buf correctly in bulk_init()
bulk: set ->size of last bulk_buf correctly in bulk_init()

Since ->size of bulk_buf was not set correctly, the assertion in
bulk_buf_copy() was triggered.

modeswitch/barrelfish,modeswitch/barrelfish,modeswitch/barrelfish,modeswitch/barrelfish,modeswitch/barrelfish