semihosting: Cleanup chardev init

Rename qemu_semihosting_connect_chardevs to
qemu_semihosting_chardev_init; pass the result
directly to qemu_semihosting_console_init.

Store the chardev in SemihostingConsole instead
of SemihostingConfig, which lets us drop
semihosting_get_chardev.

Reviewed-by: Luc Michel <lmichel@kalray.eu>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

stubs/semihost.c

@@ -65,10 +65,6 @@ void semihosting_arg_fallback(const char *file, const char *cmd)
 {
 }
 
-void qemu_semihosting_connect_chardevs(void)
-{
-}
-
-void qemu_semihosting_console_init(void)
+void qemu_semihosting_chardev_init(void)
 {
 }