We are about to enable the build without TCG, so CONFIG_SEMIHOSTING
and CONFIG_ARM_COMPATIBLE_SEMIHOSTING cannot be unconditionally set in
default.mak anymore. So reflect the change in a Kconfig.

Instead of using semihosting/Kconfig, use a target-specific file, so
that the change doesn't affect other architectures which might
implement semihosting in a way compatible with KVM.

The selection from ARM_v7M needs to be removed to avoid a cycle during
parsing.

Signed-off-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20230426180013.14814-11-farosas@suse.de
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>