crypto: caam/jr - Removed redundant vars from job ring private data

For each job ring, the variable 'ringsize' is initialised but never
used. Similarly variables 'inp_ring_write_index' and 'head' always track
the same value and instead of 'inp_ring_write_index', caam_jr_enqueue()
can use 'head' itself. Both these variables have been removed.

Signed-off-by: Vakul Garg <vakul.garg@nxp.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>