treewide: Add a function to change page permissions

For armv8 we are adding proper page permissions for the relocated U-Boot
binary. Add a weak function that can be used across architectures to change
the page permissions

Tested-by: Neil Armstrong <neil.armstrong@linaro.org> # on AML-S905X-CC
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
diff --git a/arch/arm/lib/cache.c b/arch/arm/lib/cache.c
index 516754c..dd19bd3 100644
--- a/arch/arm/lib/cache.c
+++ b/arch/arm/lib/cache.c
@@ -10,6 +10,7 @@
 #include <malloc.h>
 #include <asm/cache.h>
 #include <asm/global_data.h>
+#include <linux/errno.h>
 
 DECLARE_GLOBAL_DATA_PTR;
 
@@ -170,3 +171,8 @@
 
 	return 0;
 }
+
+int __weak pgprot_set_attrs(phys_addr_t addr, size_t size, enum pgprot_attrs perm)
+{
+	return -ENOSYS;
+}