dt-bindings: input: touchscreen: stmpe: Remove node name requirement

STMPE driver does not require a specific node name anymore, only the
compatible is checked, update binding according to this.
Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220712163345.445811-6-francesco.dolcini@toradex.comSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Documentation/devicetree/bindings/input/touchscreen/stmpe.txt

@@ -54,8 +54,7 @@ Optional properties common with MFD (deprecated):
 				1 -> 3.25 MHz
 				2 || 3 -> 6.5 MHz
 
-Node name must be stmpe_touchscreen and should be child node of stmpe node to
-which it belongs.
+Node should be child node of stmpe node to which it belongs.
 
 Note that common ADC settings of stmpe_touchscreen (child) will take precedence
 over the settings done in MFD.