arm64: dts: visconti: Add 150MHz fixed clock to TMPV7708 SoC

This clock source is referred by baudrate generators of
SPI and I2C devices.

Signed-off-by: Yuji Ishikawa <yuji2.ishikawa@toshiba.co.jp>
Link: https://lore.kernel.org/r/20211014092703.15251-2-yuji2.ishikawa@toshiba.co.jp


Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>