crypto: caam - fix RNG buffer cache alignment

The hwrng output buffers (2) are cast inside of a a struct (caam_rng_ctx)
allocated in one DMA-tagged region. While the kernel's heap allocator
should place the overall struct on a cacheline aligned boundary, the 2
buffers contained within may not necessarily align. Consenquently, the ends
of unaligned buffers may not fully flush, and if so, stale data will be left
behind, resulting in small repeating patterns.

This fix aligns the buffers inside the struct.

Note that not all of the data inside caam_rng_ctx necessarily needs to be
DMA-tagged, only the buffers themselves require this. However, a fix would
incur the expense of error-handling bloat in the case of allocation failure.

Cc: stable@vger.kernel.org
Signed-off-by: Steve Cornelius <steve.cornelius@freescale.com>
Signed-off-by: Victoria Milhoan <vicki.milhoan@freescale.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>