counter: Move counter enums to uapi header

This is in preparation for a subsequent patch implementing a character
device interface for the Counter subsystem.

Reviewed-by: David Lechner <david@lechnology.com>
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Link: https://lore.kernel.org/r/962a5f2027fafcf4f77c10e1baf520463960d1ee.1632884256.git.vilhelm.gray@gmail.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>