xen/arm: regs: Fix MISRA C 2012 Rule 20.7 violation

In macro psr_mode(), the macro parameter 'm' is used as expression and
therefore it is good to be enclosed in parentheses to prevent against
unintended expansions.

Signed-off-by: Xenia Ragiadakou <burzalodowa@gmail.com>
Reviewed-by: Rahul Singh <rahul.singh@arm.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

xen/arch/arm/include/asm/regs.h

@@ -11,7 +11,7 @@
 #include <asm/current.h>
 #include <asm/processor.h>
 
-#define psr_mode(psr,m) (((psr) & PSR_MODE_MASK) == m)
+#define psr_mode(psr,m) (((psr) & PSR_MODE_MASK) == (m))
 
 static inline bool regs_mode_is_32bit(const struct cpu_user_regs *regs)
 {