crypto: jitterentropy - change back to module_init()

"jitterentropy_rng" doesn't have any other implementations, nor is it
tested by the crypto self-tests.  So it was unnecessary to change it to
subsys_initcall.  Also it depends on the main clocksource being
initialized, which may happen after subsys_initcall, causing this error:

    jitterentropy: Initialization failed with host not compliant with requirements: 2

Change it back to module_init().

Fixes: c4741b23

 ("crypto: run initcalls for generic implementations earlier")
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>