The QuadSPI modules is flexible enough and supports single, dual, quad and octal (2 flash devices) modes of operation.
The instruction-operand issued by the programmable sequence engine provide a 2-bit field called PINS which indicates how many lines/pads to use for the
read/write (or any other) command. The possible values are:
0x0 for Single mode,
0x1 for Dual,
0x10 for Quad and
0x11 for Octal.
You can check Section 30.5.3.1 Programmable Sequence Engine in Reference Manual for more info.