gpu-compute: Add missing include in dispatcher.cc

Due to some cherry-picking onto the release-staging branch, there was a
missing "sim/sim_exit.hh" include in "src/gpu-compute/dispatcher.cc".
This was causing compilation errors.

This is being added to the v23.0.0 release as a hotfix.

Change-Id: I1043ecf5c41ad6afc0e91311b196f4801646002f
Issue-on: https://gem5.atlassian.net/browse/GEM5-1332
1 file changed