mtd: spi-nor: cadence-quadspi: add a delay in write sequence

mtd: spi-nor: cadence-quadspi: add a delay in write sequence

As per 66AK2G02 TRM[1] SPRUHY8F section 11.15.5.3 Indirect Access
Controller programming sequence, a delay equal to couple of QSPI master
clock(~5ns) is required after setting CQSPI_REG_INDIRECTWR_START bit and
writing data to the flash. Introduce a quirk flag CQSPI_NEEDS_WR_DELAY
to handle this and set this flag for TI 66AK2G SoC.

[1]http://www.ti.com/lit/ug/spruhy8f/spruhy8f.pdf

Signed-off-by: Vignesh R <vigneshr@ti.com>
Acked-by: Marek Vasut <marek.vasut@gmail.com>
Signed-off-by: Cyrille Pitchen <cyrille.pitchen@wedev4u.fr>