Bug 1369: fix type mismatch warning.
Bug 1369: fix type mismatch warning.

Returned values of omp thread id and numbers are int,
o let's use int instead of Index here.
(grafted from ec0f519aaaecf037f25e6d6580b104dc5bf437d5)

ROCmSoftwarePlatform/hipeigen,ROCmSoftwarePlatform/hipeigen,ROCmSoftwarePlatform/hipeigen,ROCmSoftwarePlatform/hipeigen