fix bidir dshot for nxp xrt boards

Cherry-picked from upstream PX4/PX4-Autopilot PR PX4#25854
Commit: c44e0be
Fixes: PX4#25853

When attempting to use bidirectional dshot on NXP i.MXRT boards,
esc_status messages would never get published. This was due to
bdshot_recv_mask being used to check the number of ready erpms,
while this mask is always set to zero before the check.

Fixed by checking bdshot_parsed_recv_mask instead.

Author: 321thijs123

platforms/nuttx/src/px4/nxp/imxrt/dshot/dshot.c

@@ -425,7 +425,7 @@ int up_bdshot_num_erpm_ready(void)
 	for (unsigned i = 0; i < DSHOT_TIMERS; ++i) {
 		// We only check that data has been received, rather than if it's valid.
 		// This ensures data is published even if one channel has bit errors.
-		if (bdshot_recv_mask & (1 << i)) {
+		if (bdshot_parsed_recv_mask & (1 << i)) {
 			++num_ready;
 		}
 	}