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/cpu/armv7m/cache.c b/arch/arm/cpu/armv7m/cache.c
index b6d08b7..8e7db73 100644
--- a/arch/arm/cpu/armv7m/cache.c
+++ b/arch/arm/cpu/armv7m/cache.c
@@ -11,6 +11,7 @@
 #include <asm/cache.h>
 #include <asm/io.h>
 #include <linux/bitops.h>
+#include <linux/errno.h>
 
 /* Cache maintenance operation registers */
 
@@ -370,3 +371,8 @@
 	dcache_enable();
 #endif
 }
+
+int __weak pgprot_set_attrs(phys_addr_t addr, size_t size, enum pgprot_attrs perm)
+{
+	return -ENOSYS;
+}