xtensa: fix kmap_prot definition

commit ff009ab6 upstream.

Replace PAGE_KERNEL with PAGE_KERNEL_EXEC to allow copy_to_user_page
invalidate icache for pages mapped with kmap.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

arch/xtensa/include/asm/highmem.h

@@ -23,7 +23,7 @@
 #define PKMAP_NR(virt)		(((virt) - PKMAP_BASE) >> PAGE_SHIFT)
 #define PKMAP_ADDR(nr)		(PKMAP_BASE + ((nr) << PAGE_SHIFT))
 
-#define kmap_prot		PAGE_KERNEL
+#define kmap_prot		PAGE_KERNEL_EXEC
 
 extern pte_t *pkmap_page_table;