NVSSPI25x driver does not work when using internal SPI CS

(Most, All?) SPI flash chips require a single SPI transaction, defined by a single CS assert/deassert, to implement a command/instruction. The NVSSPI25x driver implements separate write and read operations, bracketed by CS assert/deassert. This works with external GPIO CS usage but not with the internal SPI CS mechanism since the initial write will do assert/deassert and then the read will do another cycle.