of: base: export of_device_compatible_match() for use in modules

Modules such as net/dsa/dsa_core.ko might want to iterate through an
array of compatible strings for things such as validation (or rather,
skipping it for some potentially broken drivers).

of_device_is_compatible() is exported, by of_device_compatible_match()
isn't. Export the latter as well, so we don't have to open-code the
iteration.

Cc: Frank Rowand <frowand.list@gmail.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>