arm/Kconfig: Make TCG dependence explicit

arm/Kconfig: Make TCG dependence explicit

Replace the 'default y if TCG' pattern with 'default y; depends on
TCG'.

That makes explict that there is a dependence on TCG and enabling
these CONFIGs via .mak files without TCG present will fail earlier.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20230523180525.29994-4-farosas@suse.de
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>