mtd: spi-nor: Mask out fast read if not requested in DT

The DT bindings of "jedec,spi-nor" [1] defines "m25p,fast-read" property
to indicate that "fast read" opcode can be used to read data from the
chip instead of the usual "read" opcode.

If this property is not present in DT, mask out fast read in
spi_nor_init_params(). This change mirrors the same logic in
spi_nor_info_init_params() in drivers/mtd/spi-nor/core.c in
the Linux kernel v5.14-rc3.

[1] Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml in the kernel tree

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>