[AMDGPU] Run twoaddr tests with -early-live-intervals (#66775)

Sample test case:

%3 = V_FMAC_F32_e32 killed %0, %1, %2, implicit $mode, implicit $exec

With LiveVariables this is converted to three-address form just because
there is no "killed" flag on %2. To make it do the same thing with
LiveIntervals I added a later use of %2:

%3 = V_FMAC_F32_e32 killed %0, %1, %2, implicit $mode, implicit $exec
    S_ENDPGM 0, implicit %2