arm/Kconfig: Do not build TCG-only boards on a KVM-only build

arm/Kconfig: Do not build TCG-only boards on a KVM-only build

Move all the CONFIG_FOO=y from default.mak into "default y if TCG"
statements in Kconfig. That way they won't be selected when
CONFIG_TCG=n.

I'm leaving CONFIG_ARM_VIRT in default.mak because it allows us to
keep the two default.mak files not empty and keep aarch64-default.mak
including arm-default.mak. That way we don't surprise anyone that's
used to altering these files.

With this change we can start building with --disable-tcg.

Signed-off-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20230426180013.14814-12-farosas@suse.de
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>