sb/intel/bd82x6x: Clean up early_thermal.c

Use proper types in readXp functions, define `PCH_THERMAL_DEV`, clean up
comments a bit, and use `RCBA32_AND_OR` instead of read32/write32.

Tested with BUILD_TIMELESS=1, Asus P8Z77-V LX2 remains identical.

Change-Id: I95e054d6e52706e06e313068e61484f6cb9a64e5
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50038
Reviewed-by: Patrick Rudolph <siro@das-labor.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/southbridge/intel/bd82x6x/pch.h b/src/southbridge/intel/bd82x6x/pch.h
index 1840a2b..fa0f712 100644
--- a/src/southbridge/intel/bd82x6x/pch.h
+++ b/src/southbridge/intel/bd82x6x/pch.h
@@ -85,6 +85,7 @@
 #define PCH_EHCI1_DEV		PCI_DEV(0, 0x1d, 0)
 #define PCH_EHCI2_DEV		PCI_DEV(0, 0x1a, 0)
 #define PCH_ME_DEV		PCI_DEV(0, 0x16, 0)
+#define PCH_THERMAL_DEV		PCI_DEV(0, 0x1f, 6)
 #define PCH_PCIE_DEV_SLOT	28
 #define PCH_IOAPIC_PCI_BUS	250
 #define PCH_IOAPIC_PCI_SLOT	31