By selecting MTD_SPI_NOR for SPI_HISI_SFC_V3XX, we may introduce unmet
dependencies:

WARNING: unmet direct dependencies detected for MTD_SPI_NOR
  Depends on [m]: MTD [=m] && SPI_MASTER [=y]
  Selected by [y]:
  - SPI_HISI_SFC_V3XX [=y] && SPI [=y] && SPI_MASTER [=y] && (ARM64 && ACPI [=y] || COMPILE_TEST [=y]) && HAS_IOMEM [=y]

Since MTD_SPI_NOR is only selected by SPI_HISI_SFC_V3XX for practical
reasons - slave devices use the spi-nor driver, enabled by MTD_SPI_NOR -
just drop it.
Signed-off-by: NJohn Garry <john.garry@huawei.com>

Link: https://lore.kernel.org/r/1583948115-239907-1-git-send-email-john.garry@huawei.comSigned-off-by: NMark Brown <broonie@kernel.org>