pinctrl: bcm2835: drop irq_enable/disable callbacks

commit db1b3ece upstream.

The commit b8a19382

 ("pinctrl: bcm2835: Fix support for threaded level
triggered IRQs") assigned the irq_mask/unmask callbacks with the
already existing functions for irq_enable/disable. The wasn't completely
the right way (tm) to fix the issue, because these callbacks shouldn't
be identical. So fix this by rename the functions to represent their
intension and drop the unnecessary irq_enable/disable assigment.

Suggested-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>