dfuse: Allow direct transition to DNLOAD_IDLE on special command

It seems that the DFU 1.1 specification (Appendix A. Interface State
Summary) allows a transition from dfuIDLE (by DFU_DNLOAD request) to
dfuDNLOAD-SYNC, then to dfuDNLOAD-IDLE (by DFU_GETSTATUS request) if the
block is complete, without going via dfuDNBUSY.

For a DfuSe special command DFU_DNLOAD request like SET_ADDRESS this
could make sense. This behavior has been seen on a STM32U5A9BJ
bootloader.

Thanks to Markus Pope for analysis and initial patch.

https://sourceforge.net/p/dfu-util/tickets/145/

Signed-off-by: Tormod Volden <debian.tormod@gmail.com>

src/dfuse.c

@@ -261,7 +261,7 @@ static int dfuse_special_command(struct dfu_if *dif, unsigned int address,
 		}
 		if (firstpoll) {
 			firstpoll = 0;
-			if (dst.bState != DFU_STATE_dfuDNBUSY) {
+			if (dst.bState != DFU_STATE_dfuDNBUSY && dst.bState != DFU_STATE_dfuDNLOAD_IDLE) {
 				fprintf(stderr, "DFU state(%u) = %s, status(%u) = %s\n", dst.bState,
 				       dfu_state_to_string(dst.bState), dst.bStatus,
 				       dfu_status_to_string(dst.bStatus));