crypto: omap-sham: Enable Polling mode if DMA fails

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>
crypto: omap-sham: correct dma burst size

Each cycle of SHA512 operates on 32 data words where as
SHA256 operates on 16 data words. This needs to be updated
while configuring DMA channels. Doing the same.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>