tests: drivers: console: Skip semihosting console device testing

The semihosting console test (`drivers.console.semihost`) is currently
only supported on the ARM Cortex-M QEMU targets.

While running this test on real hardware targets is possible, there is
no standardised way for sanitycheck to validate its output, so we
filter by `CONFIG_QEMU_TARGET` to skip running it on non-QEMU targets
(including physical hardware targets with `--device-testing`).

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>