spi: zynq_[q]spi: Convert config's to macro's

Remove below config options and convert them to macros. They have never
been configured to different values than default one. And also it makes
sense to reduce the config_whitelist.
CONFIG_SYS_ZYNQ_SPI_WAIT
CONFIG_SYS_ZYNQ_QSPI_WAIT
CONFIG_XILINX_SPI_IDLE_VAL

Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>