crypto: lib/Kconfig - hide library options

Any driver that needs these library functions should already be selecting
the corresponding Kconfig symbols, so there is no real point in making
these visible.

The original patch that made these user selectable described problems
with drivers failing to select the code they use, but for consistency
it's better to always use 'select' on a symbol than to mix it with
'depends on'.

Fixes: e56e1898 ("lib/crypto: add prompts back to crypto libraries")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>