mtd: spi-nor-core: Replace MTD_SPI_NOR_USE_4K_SECTORS with SPI_FLASH_USE_4K_SECTORS

U-Boot uses CONFIG_SPI_FLASH_USE_4K_SECTORS to enable 4K small sector
support. Use that instead of MTD_SPI_NOR_USE_4K_SECTORS.

Reported-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>