Revert "Revert "mb/google/volteer: Enable PCIEXP_HOTPLUG for TCSS TBT/USB4 ports""

This reverts commit 1726fa1f0ce474cde32e8b32be34a212aff3ffba.

Reason for revert: Resource allocator is split into old(v3) and
new(v4). So, this change to enable hotplug resource allocator for
volteer can land back.

BUG=b:149186922

Change-Id: Ib6a4df610b045fbc885c70bff3698a032b79f770
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/41468
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/mainboard/google/volteer/Kconfig

@@ -19,6 +19,7 @@ config BOARD_GOOGLE_BASEBOARD_VOLTEER
 	select MAINBOARD_HAS_CHROMEOS
 	select MAINBOARD_HAS_SPI_TPM_CR50
 	select MAINBOARD_HAS_TPM2
+	select PCIEXP_HOTPLUG
 	select SOC_INTEL_TIGERLAKE
 
 if BOARD_GOOGLE_BASEBOARD_VOLTEER
@@ -72,6 +73,20 @@ config MAX_CPUS
 	int
 	default 8
 
+# Reserving resources for PCIe Hotplug as per TGL BIOS Spec (doc #611569)
+# Revision 0.7.6 Section 7.2.5.1.5
+config PCIEXP_HOTPLUG_BUSES
+	int
+	default 42
+
+config PCIEXP_HOTPLUG_MEM
+	hex
+	default 0xc200000  # 194 MiB
+
+config PCIEXP_HOTPLUG_PREFETCH_MEM
+	hex
+	default 0x1c000000 # 448 MiB
+
 config TPM_TIS_ACPI_INTERRUPT
 	int
 	default 21  # GPE0_DW0_21 (GPP_C21)