kernel: backport GD25Q256 support from 4.15

kernel: backport GD25Q256 support from 4.15

Backport below changes for GigaDevice GD25Q256 support from v4.15:

  e27072851bf7 mtd: spi-nor: add a quad_enable callback in struct flash_info
  65153846b18c mtd: spi-nor: add support for GD25Q256

This chip is used on newer Quad-E4G boards.

Before:

[    2.366493] m25p80 spi0.0: unrecognized JEDEC id bytes: c8, 40, 19
[    2.372853] m25p80: probe of spi0.0 failed with error -2

After:

[    2.371722] m25p80 spi0.0: gd25q256 (32768 Kbytes)
[    2.376694] 5 fixed-partitions partitions found on MTD device spi0.0
[    2.383043] Creating 5 MTD partitions on "spi0.0":
[    2.387824] 0x000000000000-0x000000030000 : "u-boot"
[    2.394138] 0x000000030000-0x000000031000 : "u-boot-env"
[    2.400608] 0x000000031000-0x000000040000 : "config"
[    2.406830] 0x000000040000-0x000000050000 : "factory"
[    2.413169] 0x000000050000-0x000002000000 : "firmware"

Signed-off-by: Kuan-Yi Li <kyli@abysm.org>