util/ifdtool: Add Xeon SP Lewisburg PCH platform support under IFDv2

After commit 8c082e5fe (util/ifdtool: Use -p platform name
to detect IFDv2 platform and chipset) w/o this xeon_sp/cpx would be
detected as IFDv1 and see build error.

Fixes: 8c082e5fe ("util/ifdtool: Use -p platform name to detect IFDv2 platform and chipset")
Change-Id: I444e7d35a85d9d42fc25d654e57386f38cf1ec85
Signed-off-by: Johnny Lin <johnny_lin@wiwynn.com>
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/55745
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Subrata Banik <subrata.banik@intel.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

util/ifdtool/ifdtool.h

@@ -50,6 +50,7 @@ enum ich_chipset {
 enum platform {
 	PLATFORM_APL,
 	PLATFORM_CNL,
+	PLATFORM_LBG,
 	PLATFORM_EHL,
 	PLATFORM_GLK,
 	PLATFORM_ICL,