Revert "[AArch64] Add Machine InstCombiner patterns for FMUL indexed variant"

This reverts commit cca9b598.

Buildbot reported an error for CodeGen/AArch64/machine-combiner-fmul-dup.mir:

*** Bad machine code: Virtual register killed in block, but needed live out. ***
- function:    indexed_2s
- basic block: %bb.0 entry (0x640fee8)
Virtual register %7 is used after the block.

*** Bad machine code: Virtual register defs don't dominate all uses. ***
- function:    indexed_2s
- v. register: %7
LLVM ERROR: Found 2 machine code errors.