regmap: Specify a module license

CONFIG_REGMAP_I2C/SPI are set to m when selected by a tristate config
option that's set to m. The regmap modules don't specify a license, so
fail to link to regmap_init at load time, since that is EXPORT_SYMBOL_GPL.
Fix this by specifying a license for the regmap modules.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>