pinctrl: mediatek: common-v1: Fix error checking in mtk_eint_init()

pinctrl: mediatek: common-v1: Fix error checking in mtk_eint_init()

The devm_kzalloc() function doesn't return error pointers, it returns
NULL on error.  Then on the next line it checks the same pointer again
by mistake, "->base" instead of "->base[0]".

Fixes: fe412e3a6c97 ("pinctrl: mediatek: common-v1: Fix EINT breakage on older controllers")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/aAijc10fHka1WAMX@stanley.mountain
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>