common: bootm_os: make arch_preboot_os __weak

Signed-off-by: Jeroen Hofstee <jeroen@myspectrum.nl>

common/bootm_os.c

@@ -437,11 +437,10 @@ static boot_os_fn *boot_os[] = {
 };
 
 /* Allow for arch specific config before we boot */
-static void __arch_preboot_os(void)
+__weak void arch_preboot_os(void)
 {
 	/* please define platform specific arch_preboot_os() */
 }
-void arch_preboot_os(void) __attribute__((weak, alias("__arch_preboot_os")));
 
 int boot_selected_os(int argc, char * const argv[], int state,
 		     bootm_headers_t *images, boot_os_fn *boot_fn)