Kconfig: Drop duplicate 'select SHA512' instances

When dropping SHA512_ALGO in general, we didn't catch some cases where
an option was selecting  both SHA512 and SHA512_ALGO and caused them to
select SHA512 twice.  Kconfig doesn't complain, but this is still wrong
and should be corrected.

Fixes: e60e4499 ("lib: Drop SHA512_ALGO in lieu of SHA512")
Reported-by: Andreas Schwab <schwab@suse.de>
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Signed-off-by: Tom Rini <trini@konsulko.com>