keys: cleanup dead code in Kconfig for FIPS_SIGNATURE_SELFTEST

keys: cleanup dead code in Kconfig for FIPS_SIGNATURE_SELFTEST

There is already an 'if ASYMMETRIC_KEY_TYPE' condition wrapping
FIPS_SIGNATURE_SELFTEST, making the 'depends on' statement a
duplicate dependency (dead code).

I propose leaving the outer 'if ASYMMETRIC_KEY_TYPE...endif' and removing
the individual 'depends on' statement.

This dead code was found by kconfirm, a static analysis tool for Kconfig.

Signed-off-by: Julian Braha <julianbraha@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>