loadb: Properly indicate aborted kermit transfer

When k_recv() returns zero it indicates that kermit transfer was aborted.
Function do_load_serial_bin() (caller of load_serial_bin()) interprets
value ~0 as aborted transfer, so properly propagates information about
aborted transfer from k_recv() to do_load_serial_bin().

Signed-off-by: Pali Rohár <pali@kernel.org>

cmd/load.c

@@ -535,6 +535,9 @@ static ulong load_serial_bin(ulong offset)
 		udelay(1000);
 	}
 
+	if (size == 0)
+		return ~0; /* Download aborted */
+
 	flush_cache(offset, size);
 
 	printf("## Total Size      = 0x%08x = %d Bytes\n", size, size);