regmap: fix writes to non incrementing registers

regmap: fix writes to non incrementing registers

commit 2e31aab08bad0d4ee3d3d890a7b74cb6293e0a41 upstream.

When checking if a register block is writable we must ensure that the
block does not start with or contain a non incrementing register.

Fixes: 8b9f9d4dc511 ("regmap: verify if register is writeable before writing operations")
Signed-off-by: Ben Whitten <ben.whitten@gmail.com>
Link: https://lore.kernel.org/r/20200118205625.14532-1-ben.whitten@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>