Remove gdb-ppc-power7-test.patch
    
    The test added by this patch claims to be a power7 test, however, it
    actually appears to test instructions from power7, power8, and power9.
    
    All the instructions tested by this patch are already tested by
    upstream tests:
    
      gdb.arch/powerpc-power7.exp
      gdb.arch/powerpc-power8.exp
      gdb.arch/powerpc-power9.exp
    
    As such this patch is redundant and can be removed.