arm64: Export __copy_in_user() to modules

This function may be called from loadable modules, so it needs
exporting.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: Loc Ho <lho@apm.com>

arch/arm64/kernel/arm64ksyms.c

@@ -39,6 +39,7 @@ EXPORT_SYMBOL(clear_page);
 EXPORT_SYMBOL(__copy_from_user);
 EXPORT_SYMBOL(__copy_to_user);
 EXPORT_SYMBOL(__clear_user);
+EXPORT_SYMBOL(__copy_in_user);
 
 	/* physical memory */
 EXPORT_SYMBOL(memstart_addr);