gpio: mvebu: fix potential user-after-free on probe

When mvebu_pwm_probe() fails IRQ domain is not released. Move pwm probe
before IRQ domain allocation. Add pwm cleanup code to the failure path.

Fixes: 757642f9

 ("gpio: mvebu: Add limited PWM support")
Reported-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>