ARM: dts: spear320-hmi: correct STMPE GPIO compatible

The compatible is st,stmpe-gpio.

Fixes: e2eb6918 ("ARM: SPEAr320: DT: Add SPEAr 320 HMI board support")
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Link: https://lore.kernel.org/r/20230225162237.40242-1-krzysztof.kozlowski@linaro.org


Signed-off-by: Arnd Bergmann <arnd@arndb.de>