arc: Fix CTS tests for grunt

Waiting loop has 1us delay waiting for requested changes are propagated.
This is too aggressive and Grunt and other low-end devices may
have no chance to react in specific timeout.

Bug: 265675811
Test: cts-tradefed run commandAndExit cts -m  CtsSimpleperfTestCases
      Most tests are now passing:
      Total Tests       : 540
      PASSED            : 528
      FAILED            : 12

Change-Id: Ida041674c2fea425e6d267ee6a973208da00ed71
1 file changed