spi: xilinx: increase number of retries before declaring stall

SPI devices using a (relative) slow frequency need a larger time.

For instance, microblaze running at 83.25MHz and performing a
3 bytes transaction using a 10MHz/16 = 625kHz needed this stall
value increased to at least 20. The SPI device is quite slow, but
also is the microblaze, so set this value to 32 to give it even
more margin.

Signed-off-by: Alvaro Gamez Machado <[e-mail]>
Reviewed-by: Ricardo Ribalda <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

drivers/spi/spi-xilinx.c

···
 
 		/* Read out all the data from the Rx FIFO */
 		rx_words = n_words;
-		stalled = 10;
+		stalled = 32;
 		while (rx_words) {
 			if (rx_words == n_words && !(stalled--) &&
 			    !(sr & XSPI_SR_TX_EMPTY_MASK) &&