soc/mtk_adsp: Add default console hook

Wire the default printk output to the console at boot, just to be sure
we have stdio output good enough to get tests to pass.

Signed-off-by: Andy Ross <andyross@google.com>

soc/mediatek/mtk_adsp/soc.c

@@ -3,6 +3,7 @@
  */
 
 #include <zephyr/devicetree.h>
+#include <zephyr/sys/libc-hooks.h>
 #include <string.h>
 #include <kernel_internal.h>
 
@@ -171,5 +172,8 @@ void c_boot(void)
 	val = 0xffffffff;
 	__asm__ volatile("wsr %0, INTCLEAR" :: "r"(val));
 
+	/* Default console, a driver can override this later */
+	__stdout_hook_install(arch_printk_char_out);
+
 	z_prep_c();
 }