b43legacy: Remove unnecessary MMIO in interrupt hotpath

This removes unnecessary MMIO accesses in the interrupt hotpath. The
patch by Michael Buesch for b43 has been ported to b43legacy.

Signed-off-by: Stefano Brivio <stefano.brivio@polimi.it>
Tested-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/b43legacy/b43legacy.h b/drivers/net/wireless/b43legacy/b43legacy.h
index da59ef0..19a4b0b 100644
--- a/drivers/net/wireless/b43legacy/b43legacy.h
+++ b/drivers/net/wireless/b43legacy/b43legacy.h
@@ -694,8 +694,8 @@
 	/* Reason code of the last interrupt. */
 	u32 irq_reason;
 	u32 dma_reason[6];
-	/* saved irq enable/disable state bitfield. */
-	u32 irq_savedstate;
+	/* The currently active generic-interrupt mask. */
+	u32 irq_mask;
 	/* Link Quality calculation context. */
 	struct b43legacy_noise_calculation noisecalc;
 	/* if > 0 MAC is suspended. if == 0 MAC is enabled. */