crypto: pcomp - Constify (de)compression parameters

crypto: pcomp - Constify (de)compression parameters

In testmgr, struct pcomp_testvec takes a non-const 'params' field, which is
pointed to a const deflate_comp_params or deflate_decomp_params object.  With
gcc-5 this incurs the following warnings:

In file included from ../crypto/testmgr.c:44:0:
../crypto/testmgr.h:28736:13: warning: initialization discards 'const' qualifier from pointer target type [-Wdiscarded-array-qualifiers]
   .params = &deflate_comp_params,
             ^
../crypto/testmgr.h:28748:13: warning: initialization discards 'const' qualifier from pointer target type [-Wdiscarded-array-qualifiers]
   .params = &deflate_comp_params,
             ^
../crypto/testmgr.h:28776:13: warning: initialization discards 'const' qualifier from pointer target type [-Wdiscarded-array-qualifiers]
   .params = &deflate_decomp_params,
             ^
../crypto/testmgr.h:28800:13: warning: initialization discards 'const' qualifier from pointer target type [-Wdiscarded-array-qualifiers]
   .params = &deflate_decomp_params,
             ^

Fix this by making the parameters pointer const and constifying the things
that use it.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>