[RISCV] Replace VPatBinaryV_VX_VROTATE with VPatBinaryV_VX. NFC (#178254)
VPatBinaryV_VX_VROTATE appeared to be almost exact copy and paste of
VPatBinaryV_VX except it used 'XLenVT' instead of 'vti.Scalar'.
'vti.Scalar' is 'XLenVT' for integer vectors so this wasn't a real
difference.
This change allows VV_VX or VV_VX_VI combination classes to be used,
further reducing the code.
No tablegen outputs change with this patch.