systemc: Get rid of an unused private member in sc_clock.

It's not useful, and having it makes clang upset.

Change-Id: I51366fd18a287e186c88f08af5c6ba8692779003
Reviewed-on: https://gem5-review.googlesource.com/c/13876
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>
1 file changed