mtd: spi-nor: add missing SST26* flash IC protection ops

Commit c4e88623 (mtd: spi: Switch to new SPI NOR framework)
performs switch from previous 'spi_flash' infrastructure without
proper testing/investigations which results in a regressions for
SST26 flash series.

Add missing SST26* flash IC protection ops which were introduced
previously by
Commit 3d4fed87 (mtd: sf: Add support of sst26wf* flash ICs
protection ops)

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>