Fix Issue 7196: No extra internal regs for block nodes

Fix Issue 7196: No extra internal regs for block nodes

There is some possibly obsolete code that copies the internal registers
for a GT_IND onto the address node as well. With the struct IR changes,
the block nodes (e.g. GT_STORE_BLK) also return true for OperIsIndir(),
so they were getting the internal registers copied over from their address
node. This led to an assert on Arm64.

Fix #7196