p54spi: mask value read from SPI_ADRS_DMA_WRITE_CTRL in p54spi_wait_bit

Mask value read from SPI_ADRS_DMA_WRITE_CTRL in p54spi_wait_bit.
 Without this, 'fw_upload not allowed to DMA write' is observed at both N800 and N810.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Acked-by: Christian Lamparter <chunkeey@web.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/p54/p54spi.c

@@ -171,7 +171,7 @@ static int p54spi_wait_bit(struct p54s_priv *priv, u16 reg, __le32 bits)
 
 	for (i = 0; i < 2000; i++) {
 		p54spi_spi_read(priv, reg, &buffer, sizeof(buffer));
-		if (buffer == bits)
+		if ((buffer & bits) == bits)
 			return 1;
 
 		msleep(1);