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/supermicro/x9scl/devicetree.cb b/src/mainboard/supermicro/x9scl/devicetree.cb
index 49fcff5..284d8f3 100644
--- a/src/mainboard/supermicro/x9scl/devicetree.cb
+++ b/src/mainboard/supermicro/x9scl/devicetree.cb
@@ -20,7 +20,7 @@
 			register "gen2_dec" = "0x00fc1641" # WPCM450 SuperIO (0x1600-16ff)
 			register "gen3_dec" = "0x00040ca1" # IPMI KCS (0x0ca0-0ca3)
 			register "gen4_dec" = "0x001c03e1" # 3rd UART (0x03e0-03ff)
-			register "pcie_port_coalesce" = "1"
+			register "pcie_port_coalesce" = "true"
 			register "sata_interface_speed_support" = "0x3"
 			register "sata_port_map" = "0x3f"
 			register "spi_lvscc" = "0x2005"