i2c: qup: schedule EOT and FLUSH tags at the end of transfer

The role of FLUSH and EOT tag is to flush already scheduled
descriptors in BAM HW in case of error. EOT is required only
when descriptors are scheduled in RX FIFO. If all the messages
are WRITE, then only FLUSH tag will be used.

A single BAM transfer can have multiple read and write messages.
The EOT and FLUSH tags should be scheduled at the end of BAM HW
descriptors. Since the READ and WRITE can be present in any order
so for some of the cases, these tags are not being written
correctly.

Following is one of the example

   READ, READ, READ, READ

Currently EOT and FLUSH tags are being written after each READ.
If QUP gets NACK for first READ itself, then flush will be
triggered. It will look for first FLUSH tag in TX FIFO and will
stop there so only descriptors for first READ descriptors be
flushed. All the scheduled descriptors should be cleared to
generate BAM DMA completion.

Now this patch is scheduling FLUSH and EOT only once after all the
descriptors. So, flush will clear all the scheduled descriptors and
BAM will generate the completion interrupt.

Signed-off-by: Abhishek Sahu <absahu@codeaurora.org>
Reviewed-by: Sricharan R <sricharan@codeaurora.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>