arm64: dts: imx8m*-venice-gw7: Fix TPM schema violations

Since commit 26c9d152 ("dt-bindings: tpm: Consolidate TCG TIS
bindings"), several issues are reported by "make dtbs_check" for arm64
devicetrees:

The compatible property needs to contain the chip's name in addition to
the generic "tcg,tpm_tis-spi".

tpm@1: compatible: ['tcg,tpm_tis-spi'] is too short
	from schema $id:
http://devicetree.org/schemas/tpm/tcg,tpm_tis-spi.yaml#

Fix these schema violations.

Gateworks Venice uses an Atmel ATTPM20P:
https://trac.gateworks.com/wiki/tpm

Cc: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Tim Harvey <tharvey@gateworks.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mm-venice-gw71xx.dtsi

@@ -57,7 +57,7 @@ &ecspi2 {
 	status = "okay";
 
 	tpm@1 {
-		compatible = "tcg,tpm_tis-spi";
+		compatible = "atmel,attpm20p", "tcg,tpm_tis-spi";
 		reg = <0x1>;
 		spi-max-frequency = <36000000>;
 	};

arch/arm64/boot/dts/freescale/imx8mm-venice-gw7901.dts

@@ -297,7 +297,7 @@ flash@0 {
 	};
 
 	tpm@1 {
-		compatible = "tcg,tpm_tis-spi";
+		compatible = "atmel,attpm20p", "tcg,tpm_tis-spi";
 		reg = <0x1>;
 		spi-max-frequency = <36000000>;
 	};

arch/arm64/boot/dts/freescale/imx8mp-venice-gw71xx.dtsi

@@ -68,7 +68,7 @@ &ecspi2 {
 	status = "okay";
 
 	tpm@1 {
-		compatible = "tcg,tpm_tis-spi";
+		compatible = "atmel,attpm20p", "tcg,tpm_tis-spi";
 		reg = <0x1>;
 		spi-max-frequency = <36000000>;
 	};