There is a missing break in case PIN_CONFIG_DRIVE_STRENGTH leading to
a fall-through to the PIN_CONFIG_SLEW_RATE case that performs different
checks against *arg. This looks like an unintentional missing break so
add in the break.

Detected by CoverityScan, CID#1468456, 1468459 ("Missing break in switch")

Fixes: 513d7a2f7e0f ("pinctrl: actions: Add Actions S900 pinctrl driver")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>