sb/intel: Use `bool` for PCIe coalescing option

Retype the `pcie_port_coalesce` devicetree options and related variables
to better reflect their bivalue (boolean) nature.

Change-Id: I6a4dfe277a8f83a9eb58515fc4eaa2fee0747ddb
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/60416
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-by: Felix Singer <felixsinger@posteo.net>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/mainboard/lenovo/t520/devicetree.cb b/src/mainboard/lenovo/t520/devicetree.cb
index a1e24d5..9c75231 100644
--- a/src/mainboard/lenovo/t520/devicetree.cb
+++ b/src/mainboard/lenovo/t520/devicetree.cb
@@ -55,7 +55,7 @@
 			register "gen4_dec" = "0x0c06a1"
 
 			# Enable zero-based linear PCIe root port functions
-			register "pcie_port_coalesce" = "1"
+			register "pcie_port_coalesce" = "true"
 
 			register "pcie_hotplug_map" = "{ 0, 0, 0, 1, 0, 0, 0, 0 }"