PCI: Add mask bit definition for MSI-X table

Then we can use it instead of magic number 1.
Reviewed-by: NHidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Cc: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: NSheng Yang <sheng@linux.intel.com>
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>

drivers/pci/msi.c

@@ -168,8 +168,9 @@ static u32 __msix_mask_irq(struct msi_desc *desc, u32 flag)
 	u32 mask_bits = desc->masked;
 	unsigned offset = desc->msi_attrib.entry_nr * PCI_MSIX_ENTRY_SIZE +
 						PCI_MSIX_ENTRY_VECTOR_CTRL;
-	mask_bits &= ~1;
-	mask_bits |= flag;
+	mask_bits &= ~PCI_MSIX_ENTRY_CTRL_MASKBIT;
+	if (flag)
+		mask_bits |= PCI_MSIX_ENTRY_CTRL_MASKBIT;
 	writel(mask_bits, desc->mask_base + offset);
 
 	return mask_bits;

include/linux/pci_regs.h

@@ -315,6 +315,7 @@
 #define  PCI_MSIX_ENTRY_UPPER_ADDR	4
 #define  PCI_MSIX_ENTRY_DATA		8
 #define  PCI_MSIX_ENTRY_VECTOR_CTRL	12
+#define   PCI_MSIX_ENTRY_CTRL_MASKBIT	1
 
 /* CompactPCI Hotswap Register */