i2c: meson: remove member irq from struct meson_i2c

Member irq can be replaced with a local variable in probe
because it's nowhere else accessed.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>