SPI: add 1ms sleep in wakeup()

Without this delay I had troubles with a Raspberry-Pi:
With debug enabled I could go as high as 7.8MHz but without debug I had to go lower than 500kHz otherwise I got following error:
  errorlibnfc.driver.pn532_spiUnable to wait for SPI data. (RX)
  pn53x_check_communication: Timeout
It could work occassionally faster but very unreliable.
So the delay introduced by printf() was enough to "fix" the problem, therefore this little extra sleep() in wakeup().

libnfc/drivers/pn532_spi.c

@@ -307,6 +307,7 @@ pn532_spi_wakeup(nfc_device *pnd)
   log_put(LOG_GROUP, LOG_CATEGORY, NFC_LOG_PRIORITY_DEBUG, "Got %x byte from SPI line before wakeup", spi_byte);
 
   CHIP_DATA(pnd)->power_mode = NORMAL; // PN532 will be awake soon
+  msleep(1);
 
   if (spi_byte == 0xff) {
     log_put(LOG_GROUP, LOG_CATEGORY, NFC_LOG_PRIORITY_DEBUG, "%s", "Wakeup is needed");