mtd: spinand: gigadevice: Add continuous read support

mtd: spinand: gigadevice: Add continuous read support

GD5F1GM9 supports a high-speed Continuous Read (CR) mode which allows
the entire memory array to be read out by a single read command
without re-issuing the 13h “Page Read to Cache” command for every page.

Datasheet summary
Feature register B0[3] (NR bit)
1 = Normal Read (default)
0 = Continuous Read (CR)

ECC status register 7Ch
Normal read: bits [3:0] → ECC status of last page
Continuous read: bits [7:4] → accumulated max bit-flips over the
whole sequential read operation.

Datasheet:
https://github.com/WT-886/DATASHEET/blob/main/GD5F1GM9-v1.0.pdf

Signed-off-by: Teng Wu <gigadevice2025@gmail.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>