L2SDP-489, repaired typo.

src/periph/fpga.cpp

@@ -1446,7 +1446,7 @@ bool Periph_fpga::write_xst_processing_enable(const char *data)
             reg[0] = (uint32_t)(start_bsn & 0xffffffff);
             reg[1] = (uint32_t)((start_bsn >> 32) & 0xffffffff);
             // write sheduled bsn
-            retval &= Write("mm/0/REG_BSN_SYNC_SCHEDULER_XSUB/0/start_bsn", reg);
+            retval &= Write("mm/0/REG_BSN_SYNC_SCHEDULER_XSUB/0/ctrl_start_bsn", reg);
             reg[0] = 1;
             // write ctrl_enable = 1
             retval &= Write("mm/0/REG_BSN_SYNC_SCHEDULER_XSUB/0/ctrl_enable", reg);