modules: mbedtls: bring back SHA384 support

Before mbedTLS 3.0 there was just SHA512 option, which enabled both SHA384
and SHA512 support. mbedTLS 3.0 introduced SHA384 specific option, which
means that SHA384 got unsupported after merging
commit 4e6cfb67 ("modules: mbedTLS: Bump mbedTLS to 3.0").

Introduce SHA384 Kconfig options, so that support for it can be selected in
project configuration if needed. Since SHA384 still depends on SHA512 to be
selected, add such dependency in Kconfig.

Select SHA384 support in non-generic (not configured by Kconfig) mbedTLS
config headers, so that previous (before mbedTLS 3.0 was merged) behavior
is regained.

Fixes: 4e6cfb67 ("modules: mbedTLS: Bump mbedTLS to 3.0")
Signed-off-by: Marcin Niestroj <m.niestroj@emb.dev>