spi_bitbang: always grab lock with irqs blocked

Fix a glitch reported by lockdep in the spi_bitbang code: it needs to
consistently block IRQs when holding that spinlock.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/spi/spi_bitbang.c

@@ -184,6 +184,7 @@ int spi_bitbang_setup(struct spi_device *spi)
 	struct spi_bitbang_cs	*cs = spi->controller_state;
 	struct spi_bitbang	*bitbang;
 	int			retval;
+	unsigned long		flags;
 
 	bitbang = spi_master_get_devdata(spi->master);
 
@@ -222,12 +223,12 @@ int spi_bitbang_setup(struct spi_device *spi)
 	 */
 
 	/* deselect chip (low or high) */
-	spin_lock(&bitbang->lock);
+	spin_lock_irqsave(&bitbang->lock, flags);
 	if (!bitbang->busy) {
 		bitbang->chipselect(spi, BITBANG_CS_INACTIVE);
 		ndelay(cs->nsecs);
 	}
-	spin_unlock(&bitbang->lock);
+	spin_unlock_irqrestore(&bitbang->lock, flags);
 
 	return 0;
 }