CodeGen: Set hasSideEffects = 0 on BUNDLE

The BUNDLE itself should not have side effects, and this is a property
of instructions inside the bundle. The hasProperty check already
searches for any member instructions, which was pointless since it was
overridden by this bit.

Allows me to distinguish bundles that have side effects vs. do not in
a future patch. Also fixes an unnecessary scheduling barrier in the
bundle AMDGPU uses to get PC relative addresses.

llvm-svn: 364984