m28: Properly configure the SPI flash chipselect The SPI flash is not properly detected by plain "sf probe" due to it being located on different bus and different chipselect. Fix this problem. Signed-off-by: Marek Vasut <marex@denx.de> Cc: Stefano Babic <sbabic@denx.de> Cc: Tom Rini <trini@ti.com>