gpio: pca953x: add PCAL9535 interrupt support for Galileo Gen2

Galileo Gen2 board uses the PCAL9535 as the GPIO expansion,
it is different from PCA9535 and includes interrupt mask/status registers,
The current driver does not support the interrupt registers configuration,
it causes some gpio pins cannot trigger interrupt events,
this patch fix this issue.

The original patch was submitted by
Josef Ahmad <josef.ahmad@linux.intel.com>
http://git.yoctoproject.org/cgit/cgit.cgi/meta-intel-quark/tree/recipes-kernel/linux/files/0015-Quark-GPIO-1-2-quark.patch



Signed-off-by: Yong Li <yong.b.li@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>