Sometimes the provided RSA input buffer provided is not stripped
of leading zeros. This could cause its size to be bigger than that
of the modulus, making the HW complain:

caam_jr 2142000.jr1: 40000789: DECO: desc idx 7:
Protocol Size Error - A protocol has seen an error in size. When
running RSA, pdb size N < (size of F) when no formatting is used; or
pdb size N < (F + 11) when formatting is used.

Fix the problem by stripping off the leading zero from input data
before feeding it to the CAAM accelerator.

Fixes: 8c419778 ("crypto: caam - add support for RSA algorithm")
Cc: <stable@vger.kernel.org> # 4.8+
Reported-by: Martin Townsend <mtownsend1973@gmail.com>
Link: https://lkml.kernel.org/r/CABatt_ytYORYKtApcB4izhNanEKkGFi9XAQMjHi_n-8YWoCRiw@mail.gmail.comSigned-off-by: Horia Geantă <horia.geanta@nxp.com>
Tested-by: Fabio Estevam <fabio.estevam@nxp.com>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>