gpu: nvgpu: fix MISRA violations in utils unit

Rule 21.1 states that #define and #undef shall not be used on a
reserved identifier or reserved macro name.
Rule 21.2 states that a reserved identifier or macro name shall
not be declared.
Fix violations of the above rules in utils unit.

Jira NVGPU-3878

Change-Id: I4302c498f5fb533699d2e53b9d1ffe1e7ccf53f2
Signed-off-by: ajesh <akv@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/2194035
Reviewed-by: svc-mobile-coverity <svc-mobile-coverity@nvidia.com>
Reviewed-by: svc-mobile-misra <svc-mobile-misra@nvidia.com>
GVS: Gerrit_Virtual_Submit
Reviewed-by: Alex Waterman <alexw@nvidia.com>
Reviewed-by: Vaibhav Kachore <vkachore@nvidia.com>
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

drivers/gpu/nvgpu/include/nvgpu/posix/utils.h

@@ -235,14 +235,16 @@ static inline unsigned int nvgpu_posix_hweight64(uint64_t x)
  * here.
  */
 #define __must_check		__attribute__((warn_unused_result))
-#define __maybe_unused		__attribute__((unused))
-#define __iomem
+
+#ifndef __user
 #define __user
+#else
+#error "__user already defined !!"
+#endif
+
 #define unlikely(x)	(x)
 #define likely(x)	(x)
 
-#define __stringify(x)		#x
-
 /*
  * Prevent compiler optimizations from mangling writes. But likely most uses of
  * this in nvgpu are incorrect (i.e unnecessary).
@@ -257,8 +259,6 @@ static inline unsigned int nvgpu_posix_hweight64(uint64_t x)
 	const typeof(((type *)0)->member) *__mptr = (ptr);    \
 	(type *)((char *)__mptr - offsetof(type, member)); })
 
-#define __packed __attribute__((packed))
-
 #define MAX_ERRNO	4095
 
 #define ERESTARTSYS ERESTART