linux_compat: remove cpu_relax() define

The macro cpu_relax() is defined by several headers in different
ways.

arch/{arm,avr32,mips}/include/asm/processor.h defines it as follows:
  #define cpu_relax()	barrier()

On the other hand, include/linux/compat.h defines it as follows:
  #define cpu_relax() do {} while (0)

If both headers are included from the same source file, the warning
  warning: "cpu_relax" redefined [enabled by default]
is displayed.

It effectively makes it impossible to include <linux/compat.h>
from some sources.  Drop the latter.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: NHeiko Schocher <hs@denx.de>
Acked-by: NSimon Glass <sjg@chromium.org>
Reviewed-by: NLukasz Majewski <l.majewski@samsung.com>

drivers/usb/musb-new/musb_gadget_ep0.c

@@ -43,6 +43,7 @@
 #else
 #include <common.h>
 #include "linux-compat.h"
+#include <asm/processor.h>
 #endif
 
 #include "musb_core.h"

include/linux/compat.h

@@ -315,8 +315,6 @@ struct notifier_block {};
 
 typedef unsigned long dmaaddr_t;
 
-#define cpu_relax() do {} while (0)
-
 #define pm_runtime_get_sync(dev) do {} while (0)
 #define pm_runtime_put(dev) do {} while (0)
 #define pm_runtime_put_sync(dev) do {} while (0)