regulator: Add binding for TCS4525

Add a compatible string to support TCS4525/TCS4526 devices,
which are compatible with Fairchild FAN53555 regulators.

Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Link: https://lore.kernel.org/r/20210421210338.43819-2-ezequiel@collabora.com
Signed-off-by: Mark Brown <broonie@kernel.org>