crypto: jitter - replace ARRAY_SIZE definition with header include

The ARRAY_SIZE macro is already defined in linux/array_size.h

This patch replaces the ARRAY_SIZE definition in jitterentropy.c with
an include, to make the code cleaner, and help reduce the number of
duplicate ARRAY_SIZE definitions in the codebase.

Signed-off-by: Ruben Wauters <rubenru09@aol.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>