mb/google/cherry: Initialize DPM in romstage

Add initialization of DPM drvier used by DRAM calibration test.

Signed-off-by: Ryan Chuang <ryan.chuang@mediatek.corp-partner.google.com>
Change-Id: I8bd10864267dfa4db8528d40483eccee2d05c1d3
Reviewed-on: https://review.coreboot.org/c/coreboot/+/55775
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Yu-Ping Wu <yupingso@google.com>

src/mainboard/google/cherry/mainboard.c

@@ -10,6 +10,7 @@
 #include <framebuffer_info.h>
 #include <gpio.h>
 #include <soc/ddp.h>
+#include <soc/dpm.h>
 #include <soc/dptx.h>
 #include <soc/gpio.h>
 #include <soc/i2c.h>
@@ -193,6 +194,9 @@ static void mainboard_init(struct device *dev)
 	configure_sdcard();
 	setup_usb_host();
 
+	if (dpm_init())
+		printk(BIOS_ERR, "dpm init failed, DVFS may not work\n");
+
 	if (spm_init())
 		printk(BIOS_ERR, "spm init failed, system suspend may not work\n");