Revert "mtd: spi-nor: add support to non-uniform SPI NOR flash memories"

This reverts commit 721c908.

Revert in order to use the latest version of non-uniform erase support
for spi-nor flash memories. Will be replaced with the patchset from:
https://lkml.org/lkml/2018/7/12/664

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>

Author: ambarus