x86/pci: address violation of MISRA C Rule 20.7

MISRA C Rule 20.7 states: "Expressions resulting from the expansion
of macro parameters shall be enclosed in parentheses". Therefore, some
macro definitions should gain additional parentheses to ensure that all
current and future users will be safe with respect to expansions that
can possibly alter the semantics of the passed-in macro parameter.

No functional change.

Signed-off-by: Nicola Vetrini <nicola.vetrini@bugseng.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

xen/arch/x86/include/asm/pci.h

@@ -8,10 +8,10 @@
 #define CF8_ADDR_HI(cf8) (  ((cf8) & 0x0f000000U) >> 16)
 #define CF8_ENABLED(cf8) (!!((cf8) & 0x80000000U))
 
-#define IS_SNB_GFX(id) (id == 0x01068086 || id == 0x01168086 \
-                        || id == 0x01268086 || id == 0x01028086 \
-                        || id == 0x01128086 || id == 0x01228086 \
-                        || id == 0x010A8086 )
+#define IS_SNB_GFX(id) ((id) == 0x01068086 || (id) == 0x01168086 \
+                        || (id) == 0x01268086 || (id) == 0x01028086 \
+                        || (id) == 0x01128086 || (id) == 0x01228086 \
+                        || (id) == 0x010A8086 )
 
 struct arch_pci_dev {
     vmask_t used_vectors;