semihosting: Create qemu_semihosting_console_write

Will replace qemu_semihosting_console_{outs,outc},
but we need more plumbing first.

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

linux-user/semihost.c

@@ -76,3 +76,8 @@ int qemu_semihosting_console_read(CPUState *cs, void *buf, int len)
 
     return ret;
 }
+
+int qemu_semihosting_console_write(void *buf, int len)
+{
+    return fwrite(buf, 1, len, stderr);
+}