ANDROID: fips140: require 'm' to enable CRYPTO_FIPS140_MOD

CONFIG_CRYPTO_FIPS140_MOD builds a loadable kernel module when set to
'y'.  That's very unusual, as it doesn't follow the convention of
loadable modules being 'm'.

I'm guessing that the reason that a bool was used instead of a tristate
is because this functionality is not supported built-in, so there are
only two allowed settings: disabled or modular.

However, there's actually a way to express that in the kconfig language:
a tristate that depends on 'm'.  Let's do it that way.

This also eliminates the need to explicitly depend on MODULES.

(Note: I decided to keep MOD in the name, since the word "module" in
"FIPS 140 cryptographic module" is a different meaning of "module", and
I didn't want to bother renaming CRYPTO_FIPS140_MOD_EVAL_TESTING too.)

Bug: 188620248
Change-Id: Ib195d64d68c23ca93dd244d9ac77255992870424
Signed-off-by: Eric Biggers <ebiggers@google.com>