If the destination register doesn't equal the input register, using it
to temporarily hold the immediate value is fair game as it'll be
overwritten with the result of the multiplication anyway. This can
slightly reduce register pressure.
Before:
0x52800659 mov w25, #0x32
0x1b197f5b mul w27, w26, w25
After:
0x5280065b mov w27, #0x32
0x1b1b7f5b mul w27, w26, w27