crypto: brcm - Support more FlexRM rings than SPU engines.

Enhance code to generically support cases where DMA rings
are greater than or equal to number of SPU engines.
New hardware has underlying DMA engine-FlexRM with 32 rings
which can be used to communicate to any of the available
10 SPU engines.

Signed-off-by: Raveendra Padasalagi <raveendra.padasalagi@broadcom.com>
Reviewed-by: Scott Branden <scott.branden@broadcom.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>