mtd: spinand: add SPI-NAND MTD resume handler

After power up, all SPI NAND's blocks are locked. Only read operations
are allowed, write and erase operations are forbidden.
The SPI NAND framework unlocks all the blocks during its initialization.

During a standby low power, the memory is powered down, losing its
configuration.
During the resume, the QSPI driver state is restored but the SPI NAND
framework does not reconfigured the memory.

This patch adds SPI-NAND MTD PM handlers for resume ops.
SPI NAND resume op re-initializes SPI NAND flash to its probed state.

Signed-off-by: Christophe Kerello <christophe.kerello@foss.st.com>
Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20210602094913.26472-4-patrice.chotard@foss.st.com