arm64: dts: imx8mp-venice-gw74xx: fix TPM SPI frequency

The IMX8MPDS Table 37 [1] shows that the max SPI master read frequency
depends on the pins the interface is muxed behind with ECSPI2
muxed behind ECSPI2 supporting up to 25MHz.

Adjust the spi-max-frequency based on these findings.

[1] https://www.nxp.com/webapp/Download?colCode=IMX8MPIEC



Fixes: 531936b2 ("arm64: dts: imx8mp-venice-gw74xx: update to revB PCB")
Cc: stable@vger.kernel.org
Signed-off-by: Tim Harvey <tharvey@gateworks.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>