mtd: spi-nor: manufacturers: Use spi_nor_read_id() core method

Use spi_nor_read_id() core method to avoid duplication of code. Now the ID
is read on the full SPI_NOR_MAX_ID_LEN instead of
round_up(nor->info->id_len, 2), but it doesn't harm to read more ID bytes,
so the change comes with no secondary effects. dev_dbg messages in case
spi_nor_read_id() fails, will be added in a further patch after we split
the octal DTR enable/disable methods.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
Reviewed-by: Pratyush Yadav <p.yadav@ti.com>
Reviewed-by: Michael Walle <michael@walle.cc>
Link: https://lore.kernel.org/r/20220420103427.47867-6-tudor.ambarus@microchip.com