For writing input buffer into DATA_IN register current driver
has the following state machine:
-> if input buffer < 9 : use fallback driver
-> else if input buffer < block size : Copy input buffer into data_in regs
-> else use dma transfer.

In cases where requesting for DMA channels fails for some reason,
or channel numbers are not provided in DT or platform data, probe
also fails. Instead of returning from driver use cpu polling mode.
In this mode processor polls on INPUT_READY bit and writes data into
data_in regs when it equals 1. This operation is repeated until the
length of message.

Now the state machine looks like:
-> if input buffer < 9 : use fallback driver
-> else if input buffer < block size : Copy input buffer into data_in regs
-> else if dma enabled: use dma transfer
	   else use cpu polling mode.
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>