dt-bindings: pinctrl: qcom,sa8775p-tlmm: add gpio function constant

Alternative function 'gpio' is not listed in the constants for pin
configuration, so adding this constant to the list.

Cc: stable@vger.kernel.org
Fixes: 9a2aaee ("dt-bindings: pinctrl: describe sa8775p-tlmm")
Signed-off-by: Shazad Hussain <quic_shazhuss@quicinc.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230719110344.19983-1-quic_shazhuss@quicinc.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Author: Shazad Hussain

Documentation/devicetree/bindings/pinctrl/qcom,sa8775p-tlmm.yaml

@@ -87,7 +87,7 @@ $defs:
                 emac0_mdc, emac0_mdio, emac0_ptp_aux, emac0_ptp_pps, emac1_mcg0,
                 emac1_mcg1, emac1_mcg2, emac1_mcg3, emac1_mdc, emac1_mdio,
                 emac1_ptp_aux, emac1_ptp_pps, gcc_gp1, gcc_gp2, gcc_gp3,
-                gcc_gp4, gcc_gp5, hs0_mi2s, hs1_mi2s, hs2_mi2s, ibi_i3c,
+                gcc_gp4, gcc_gp5, gpio, hs0_mi2s, hs1_mi2s, hs2_mi2s, ibi_i3c,
                 jitter_bist, mdp0_vsync0, mdp0_vsync1, mdp0_vsync2, mdp0_vsync3,
                 mdp0_vsync4, mdp0_vsync5, mdp0_vsync6, mdp0_vsync7, mdp0_vsync8,
                 mdp1_vsync0, mdp1_vsync1, mdp1_vsync2, mdp1_vsync3, mdp1_vsync4,