soc/intel/../thermal: Fix return type of `pch_get_ltt_value()`

This patch modifies the pch_get_ltt_value() function return type from
uint16_t to uint32_t to accommodate platforms with more than one thermal
threshold.

For example: Alder Lake PCH Trip Point = T2L | T1L | T0L
where T2L > T1L > T0L.

BUG=b:193774296

Change-Id: I5f46ccb457b9cfebf13a512eabb3fb0fab8adb39
Signed-off-by: Subrata Banik <subrata.banik@intel.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/59311
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: EricR Lai <ericr_lai@compal.corp-partner.google.com>

src/soc/intel/common/block/thermal/thermal.c

@@ -23,7 +23,7 @@ static uint8_t get_thermal_trip_temp(void)
 }
 
 /* PCH Low Temp Threshold (LTT) */
-static uint16_t pch_get_ltt_value(struct device *dev)
+static uint32_t pch_get_ltt_value(struct device *dev)
 {
 	uint8_t thermal_config;