Added posted writes (read after writes) to effect the
change immediately for channel confiuration and channel
enable register

Disable the channel to purge receieve data in TX_ONLY
mode transfer otherwise rx data will get affected by
the next immediate RX_ONLY mode transfer

Wait for the EOT bit to be set after last byte has been
loaded to TX shift register in the the TX_ONLY mode.This
ensures TX data has been completely shifted out

Disable the channel in RX_ONLY mode before reading the
last data from  RXX register to prevent the SPI slave
to transmit next word
Signed-off-by: NAjoy Kumar Das <akdas75@yahoo.in>
Cc: Tom Rini <trini@ti.com>
Cc: jacopo mondi <j.mondi@voltaelectronics.com>