regmap: Add support for padding between register and address

Some devices, especially those with high speed control interfaces, require
padding between the register and the data. Support this in the regmap API
by providing a pad_bits configuration parameter.

Only devices with integer byte counts are supported.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/base/regmap/internal.h

@@ -22,6 +22,7 @@ struct regcache_ops;
 struct regmap_format {
 	size_t buf_size;
 	size_t reg_bytes;
+	size_t pad_bytes;
 	size_t val_bytes;
 	void (*format_write)(struct regmap *map,
 			     unsigned int reg, unsigned int val);