gpio: wcd934x: Fix shift-out-of-bounds error

gpio: wcd934x: Fix shift-out-of-bounds error

bit-mask for pins 0 to 4 is BIT(0) to BIT(4) however we ended up with BIT(n - 1)
which is not right, and this was caught by below usban check

UBSAN: shift-out-of-bounds in drivers/gpio/gpio-wcd934x.c:34:14

Fixes: 90a9a6ad0e73 ("gpio: wcd934x: Add support to wcd934x gpio controller")
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>