Furthermore, RX_EOF_EN should only be set when SPI Slave is configured
for segment transfer mode and the "ms_data_bitlen" field is configured
to control the "IN_SUC_EOF" interrupt. Since "ms_data_bitlen" is not
set anymore for S2, C3 and S3, "RX_EOF_EN" should be cleared.
MOSI and MISO enablement were conditioned to the existence of TX
and RX buffers, respectively. This is valid for the SPI Master,
but for the SPI Slave the opposite is expected.
