UPSTREAM: regmap: drop cache if the bus transfer error

UPSTREAM: regmap: drop cache if the bus transfer error

regmap_write
->_regmap_raw_write
-->regcache_write first and than use map->bus->write to write i2c or spi
But if the i2c or spi transfer failed, But the cache is updated, So if I use
regmap_read will get the cache data which is not the real register value.

Change-Id: Iae06edf8a2a50d2561d351a8398bd3140904630c
Signed-off-by: Elaine Zhang <zhangqing@rock-chips.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
(cherry picked from
 git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regmap.git
 commit 815806e39bf6f7e7b34875d4a9609dbe76661782)