regmap: cache: Make sure to sync the last register in a block

regcache_sync_block_raw_flush() expects the address of the register after last
register that needs to be synced as its parameter. But the last call to
regcache_sync_block_raw_flush() in regcache_sync_block_raw() passes the address
of the last register in the block. This effectively always skips over the last
register in a block, even if it needs to be synced. In order to fix it increase
the address by one register.

The issue was introduced in commit 75a5f89f

 ("regmap: cache: Write consecutive
registers in a single block write").

Cc: stable@vger.kernel.org # 3.10+
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@linaro.org>