This commit enables test_spi_loopback sample application for
Nucleo_F207zg. test_spi_loopback was executed under the following case
sceanarios on SPI-1:
a. With DMA
b. No DMA - No Interrrupts
c. No DMA - Interrupts Enabled
Signed-off-by: Krishna Mohan Dani <krishnamohan.d@hcl.com>