Was asserting when checking for uses of dead defs as it wasn't allowing for
This was shown in the case (for AMDGPU) where:
%vreg79:sub3<def,dead,tied3> = V_MAC_F32_e32 %vreg914<undef>, %vreg901,
and vreg79:sub0 vreg79:sub1 are subseqently used, but sub3 is not - firing the
Modified the check to make sure that it only checks for uses of the same lane.