mtd: spi-nor: Set default Quad Enable method for ISSI flashes

Set the default Quad Enable method for ISSI flashes. Used for
ISSI flashes (IS25WP256D-JMLE) that do not support SFDP tables
and can not determine the Quad Enable method by parsing BFPT.

Based on code originally written by Wesley Terpstra <wesley@sifive.com>
and/or Palmer Dabbelt <palmer@sifive.com>
https://github.com/riscv/riscv-linux/commit/c94e267766d62bc9a669611c3d0c8ed5ea26569b



Signed-off-by: Sagar Shrikant Kadam <sagar.kadam@sifive.com>
[tudor.ambarus@microchip.com:
- rebase, split and adapt for latest spi-nor/next,
- use PMC CFI ID for ISSI. According to JEP106BA, "Programmable Micro Corp"
  changed its name to Integrated Silicon Solution (ISSI)]
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: Vignesh Raghavendra <vigneshr@ti.com>