gpu: nvgpu: add more coverage to SYNC UT

This patch adds the following code coverage
1) Add a test to fail the allocation of syncpt_name correctly.
2) Add a test that covers all three branches of get_sync_ro_map
3) Add entry into the SWUTS.h and SWUTS.sources
4) Add test entries in the required_tests.json file
5) add nvgpu_safe_add_u64 to fix cert-C INT30 violation

Jira NVGPU-913

Change-Id: If0ccc9a9314494af1a663eb8ef37a68644c18453
Signed-off-by: Debarshi Dutta <ddutta@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/c/linux-nvgpu/+/2267389
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>

userspace/SWUTS.h

@@ -76,6 +76,7 @@
  *   - @ref SWUTS-fifo-tsg-gv11b
  *   - @ref SWUTS-fifo-userd-gk20a
  *   - @ref SWUTS-fifo-usermode-gv11b
+ *   - @ref SWUTS-nvgpu-sync
  *   - @ref SWUTS-init
  *   - @ref SWUTS-intr
  *   - @ref SWUTS-interface-atomic