gdb.base/watchpoint-running.exp: Run sw watch tests even if no hw watch

The code in gdb.base/watchpoint-running.exp that is trying to skip
testing with hardware watchpoints also skips testing with software
watchpoints if hardware watchpoints aren't supported by the target.
This fixes it.

Change-Id: Iaed62ac827b32b4fd73b732ad81fa4a5aa5784ba