crypto: pcomp - pcompress.c should include crypto/internal/compress.h

make C=1:
| crypto/pcompress.c:77:5: warning: symbol 'crypto_register_pcomp' was not declared. Should it be static?
| crypto/pcompress.c:89:5: warning: symbol 'crypto_unregister_pcomp' was not declared. Should it be static?

Signed-off-by: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>