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

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

Since commit 26c9d152ebf3 ("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>