gpio: ws16c48: Fix off-by-one error in WS16C48 resource region extent

The WinSystems WS16C48 I/O address region spans offsets 0x0 through 0xA,
which is a total of 11 bytes. Fix the WS16C48_EXTENT define to the
correct value of 11 so that access to necessary device registers is
properly requested in the ws16c48_probe() callback by the
devm_request_region() function call.

Fixes: 2c05a0f2 ("gpio: ws16c48: Implement and utilize register structures")
Cc: stable@vger.kernel.org
Cc: Paul Demetrotion <pdemetrotion@winsystems.com>
Signed-off-by: William Breathitt Gray <william.gray@linaro.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>