mtd: spi-nor: Rename SPI_ADVANCE to SPI_STACKED_PARALLEL

mtd: spi-nor: Rename SPI_ADVANCE to SPI_STACKED_PARALLEL

The SPI_ADVANCE description does not explain what the switch does.
It does not have anything to do with any advanced functionality, it
only gates off support for stacked and parallel SPI NORs. Rename the
Kconfig symbol, update description, and move it right next to Xilinx
hardware as it seems to be specific to this hardware. Make sure the
symbol is also protected by if DM_SPI in Kconfig.

Fixes: 5d40b3d384dc ("mtd: spi-nor: Add parallel and stacked memories support")
Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>