ScheduleDAGInstrs should toggle kill flags on bundled instrs.

ScheduleDAGInstrs wasn't setting or clearing the kill flags on instructions inside bundles.  This led to code such as this

%R3<def> = t2ANDrr %R0
BUNDLE %ITSTATE<imp-def,dead>, %R0<imp-use,kill>
  t2IT 1, 24, %ITSTATE<imp-def>
  R6<def,tied6> = t2ORRrr %R0<kill>, ...

being transformed to

BUNDLE %ITSTATE<imp-def,dead>, %R0<imp-use>
  t2IT 1, 24, %ITSTATE<imp-def>
  R6<def,tied6> = t2ORRrr %R0<kill>, ...
%R3<def> = t2ANDrr %R0<kill>

where the kill flag was removed from the BUNDLE instruction, but not the t2ORRrr inside it.  The verifier then thought that
R0 was undefined when read by the AND.

This change make the toggleKillFlags method also check for bundles and toggle flags on bundled instructions.
Setting the kill flag is special cased as we only want to set the kill flag on the last instruction in the bundle.

llvm-svn: 236428