[][MT7981 SPIM NAND: backport gigadevice.c of kernel v6.4 to v5.4]

[Description]
Add new serial gigadevice nand, and fix dummy byte issue, align with
kernel v6.4, and remove unnecessary device support.

source code link:
https://elixir.bootlin.com/linux/v6.4.9/source/drivers/mtd/nand/spi/gigadevice.c

[Release-log]
N/A

Change-Id: I25701d600439d546d876142a812d9ec7b8bbc266
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/7871637
8 files changed