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>

src/mainboard/google/jecht/devicetree.cb

@@ -38,7 +38,7 @@ chip soc/intel/broadwell
 			register "pcie_port_force_aspm" = "0x10"
 
 			# Enable port coalescing
-			register "pcie_port_coalesce" = "1"
+			register "pcie_port_coalesce" = "true"
 
 			# Disable PCIe CLKOUT 1,5 and CLKOUT_XDP
 			register "icc_clock_disable" = "0x01220000"