target/arm: fix handling of HLT semihosting in system mode

target/arm: fix handling of HLT semihosting in system mode

The check semihosting_enabled() wants to know if the guest is
currently in user mode. Unlike the other cases the test was inverted
causing us to block semihosting calls in non-EL0 modes.

Cc: qemu-stable@nongnu.org
Fixes: 19b26317e9 (target/arm: Honour -semihosting-config userspace=on)
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>