Introduce FLASHPROG_FLAG_NON_VOLATILE_WRSR

Add a new flag to our flash context that tells us if we should use
volatile or non-volatile status-register writes by default. Use it
in the write-protection API. The logic to disable block protection
automatically stays as is for now, until we have established tools
to manually control the protection.

Change-Id: Ie9a41b6404991075e2bf76bcffbd4e9887c62c79
Signed-off-by: Nico Huber <nico.h@gmx.de>
diff --git a/include/flash.h b/include/flash.h
index 9743e3e..ed4a373 100644
--- a/include/flash.h
+++ b/include/flash.h
@@ -453,6 +453,7 @@
 		bool force_boardmismatch;
 		bool verify_after_write;
 		bool verify_whole_chip;
+		bool non_volatile_wrsr;
 	} flags;
 	/* We cache the state of the extended address register (highest byte
            of a 4BA for 3BA instructions) and the state of the 4BA mode here.