regmap: Apply optional delay in multi_reg_write/register_patch

Add an optional delay_us field in reg_sequence to allow the client to
specify a delay (in microseconds) to be applied after any given write
in a sequence of writes.

We treat a delay in a sequence the same way we treat a page change as
they are logically similar in that you can coalesce all write before
a delay (in the same way you can coalesce all writes before a page
change is needed)

Signed-off-by: Nariman Poushin <nariman@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index c9ef2ec..5a7cf21 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -51,14 +51,17 @@
 };
 
 /**
- * Register/value pairs for sequences of writes
+ * Register/value pairs for sequences of writes with an optional delay in
+ * microseconds to be applied after each write.
  *
  * @reg: Register address.
  * @def: Register value.
+ * @delay_us: Delay to be applied after the register write in microseconds
  */
 struct reg_sequence {
 	unsigned int reg;
 	unsigned int def;
+	unsigned int delay_us;
 };
 
 #ifdef CONFIG_REGMAP