hwrng: cctrng - Make some symbols static

Fix the following sparse warnings:

drivers/char/hw_random/cctrng.c:316:6: warning: symbol
'cc_trng_compwork_handler' was not declared. Should it be static?
drivers/char/hw_random/cctrng.c:451:6: warning: symbol
'cc_trng_startwork_handler' was not declared. Should it be static?

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zou Wei <zou_wei@huawei.com>
Acked-by: Hadar Gat <hadar.gat@arm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>