gpu: nvgpu: fix misra 2.5 violations

MISRA Advisory Rule 2.5 states that a project should not contain unused
macro declarations.

While most of the violations in the nvgpu driver are due to unused
macros from hw headers, devinit-related headers, etc. there is a small
number that are due to things like:

 * macros not being used when they could/should be
 * macros in C files that are really not referenced
 * CPP build flag mismatches

This change eliminates such violations from the following:

 * replace constants with existing macros in timeout conversion code
 * wrap nvgpu_gmmu_dbg macro #defines in #ifdef CONFIG_NVGPU_TRACE/#endif
 * wrap MAX_MC_INTR_REGS #define in #ifdef CONFIG_NVGPU_NON_FUSA/#endif
 * remove unused FECS_MAILBOX_0_ACK_RESTORE from runlist code
 * wrap BACKTRACE_MAXSIZE macro with #ifndef _QNX_SOURCE/#endif

Jira NVGPU-3178

Change-Id: I2bc72f706d7af3f8e7b062126e8543d0dc8ac250
Signed-off-by: Scott Long <scottl@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/c/linux-nvgpu/+/2284419
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: svc-mobile-coverity <svc-mobile-coverity@nvidia.com>
Reviewed-by: svc-mobile-misra <svc-mobile-misra@nvidia.com>
Reviewed-by: svc-mobile-cert <svc-mobile-cert@nvidia.com>
Reviewed-by: Vedashree Vidwans <vvidwans@nvidia.com>
Reviewed-by: Sagar Kamble <skamble@nvidia.com>
Reviewed-by: Adeel Raza <araza@nvidia.com>
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>
GVS: Gerrit_Virtual_Submit

drivers/gpu/nvgpu/os/posix/bug.c

@@ -35,7 +35,9 @@
 #include <signal.h>
 #endif
 
+#ifndef _QNX_SOURCE
 #define BACKTRACE_MAXSIZE 1024
+#endif
 
 struct nvgpu_bug_desc {
 	bool in_use;