mtd: spi-nor: Remove debugfs entries that duplicate sysfs entries

SPI NOR sysfs defines partname and jedec_id device attributes, which
duplicate the information from debugfs. Since the sysfs directory
structure and the attributes in each directory define an ABI between the
kernel and user space, thus it can never be removed, remove the debugfs
entries so that we don't duplicate the information.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: Pratyush Yadav <p.yadav@ti.com>
Link: https://lore.kernel.org/r/20211217122636.474976-2-tudor.ambarus@microchip.com