xen/public: fix violations of MISRA C:2012 Rule 7.2

The xen sources contains violations of MISRA C:2012 Rule 7.2 whose
headline states:
"A 'u' or 'U' suffix shall be applied to all integer constants
that are represented in an unsigned type".

Add the 'U' suffix to integers literals with unsigned type.

For the sake of uniformity, the following changes are made:
- add the 'U' suffix to integer constants before the '?' operator

Signed-off-by: Gianluca Luparini <gianluca.luparini@bugseng.com>
Signed-off-by: Simone Ballarin <simone.ballarin@bugseng.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

xen/include/public/io/ring.h

@@ -36,11 +36,11 @@
 typedef unsigned int RING_IDX;
 
 /* Round a 32-bit unsigned constant down to the nearest power of two. */
-#define __RD2(_x)  (((_x) & 0x00000002) ? 0x2                  : ((_x) & 0x1))
-#define __RD4(_x)  (((_x) & 0x0000000c) ? __RD2((_x)>>2)<<2    : __RD2(_x))
-#define __RD8(_x)  (((_x) & 0x000000f0) ? __RD4((_x)>>4)<<4    : __RD4(_x))
-#define __RD16(_x) (((_x) & 0x0000ff00) ? __RD8((_x)>>8)<<8    : __RD8(_x))
-#define __RD32(_x) (((_x) & 0xffff0000) ? __RD16((_x)>>16)<<16 : __RD16(_x))
+#define __RD2(x)  (((x) & 0x00000002U) ? 0x2                     : ((x) & 0x1))
+#define __RD4(x)  (((x) & 0x0000000cU) ? __RD2((x) >> 2) << 2    : __RD2(x))
+#define __RD8(x)  (((x) & 0x000000f0U) ? __RD4((x) >> 4) << 4    : __RD4(x))
+#define __RD16(x) (((x) & 0x0000ff00U) ? __RD8((x) >> 8) << 8    : __RD8(x))
+#define __RD32(x) (((x) & 0xffff0000U) ? __RD16((x) >> 16) << 16 : __RD16(x))
 
 /*
  * Calculate size of a shared ring, given the total available space for the