regmap: provide helpers for simple bit operations

In many instances regmap_update_bits() is used for simple bit setting
and clearing. In these cases the last argument is redundant and we can
hide it with a static inline function.

This adds three new helpers for simple bit operations: set_bits,
clear_bits and test_bits (the last one defined as a regular function).

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: David S. Miller <davem@davemloft.net>